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3 Invitation and intervention

From: International Law and the Use of Force (4th Edition)

Christine Gray

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2022. All Rights Reserved. Subscriber: null; date: 16 May 2022

Terrorism — Use of force, war, peace and neutrality

(p. 75) Invitation and intervention

It is clear that Article 2(4), drafted in response to the Second World War, was addressed to inter-state conflicts. It says ‘all Member States shall refrain in their international relations from the threat or use of force’. Internal conflicts were seen as a domestic matter except insofar as they might constitute a threat to international peace and security under Chapter VII of the UN Charter.1 But in fact large-scale inter-state conflicts have been exceptional since 1945; most inter-state conflicts have been limited to border actions. More common have been civil wars, whether purely civil or fuelled by outside involvement or which have spilled over into neighbouring states.2 As well as direct intervention in civil wars through their regular armies, states have used indirect intervention through support to irregular forces, and also more limited forms of intervention. This chapter will focus on the law applicable to the use of force and intervention in such conflicts.

The rules prohibiting forcible intervention have been developed through General Assembly resolutions designed to elaborate on the UN Charter rules on the use of force and to supplement the express prohibitions of intervention in the constituent instruments of the major regional organizations.3

An early general provision was included in General Assembly Resolution 375 (1949) on the Rights and Duties of States; this said that every state has the duty to refrain from intervention in the internal or external affairs of any other state and that every state has the duty to refrain from fomenting civil strife in the territory of another state and to prevent the organization within its territory of (p. 76) activities calculated to foment such civil strife. Similar provision was included in Resolution 2131 (1965) on the Inadmissibility of Intervention; this said: ‘No state has the right to intervene, directly or indirectly, for any reason whatever, in the internal or external affairs of any other state. Consequently, armed intervention and all other forms of interference or attempted threats against the personality of the state or against its political, economic, and cultural elements, are condemned.’ The 1970 Declaration on Friendly Relations (Resolution 2625) followed the same approach. It spelled out the content of the prohibition of the use of force as regards civil conflict: ‘Every state has the duty to refrain from organizing, instigating, assisting or participating in acts of civil strife or terrorist acts in another State or acquiescing in organized activities within its territory directed towards the commission of such acts, when the acts referred to in the present paragraph involve a threat or use of force.’ The duty of non-intervention added to this the duty not to foment, finance, incite, or tolerate subversive, terrorist, or armed activities directed towards the violent overthrow of the regime of another state and the duty not to interfere in civil strife in another state.

The ICJ in the Nicaragua case and in Armed Activities on the Territory of Congo confirmed that these provisions of the Declaration on Friendly Relations were declaratory of customary international law.4 Thus, the status of the rules on forcible intervention is not controversial; it was their application that led to fundamental divisions during the Cold War when the superpowers and others waged proxy wars in Africa, Latin America, and Asia. These divisions as to the application of the law on intervention are also apparent in more recent conflicts, including the proxy war in Syria between regional rivals Saudi Arabia and Iran. Chapter 2 centred on the debate as to the proper interpretation of Article 2(4); this chapter will show that in the vast majority of cases of forcible intervention in a civil war it is not the interpretation but the application of the law that leads to difficulty. During the Cold War the ICJ set out the law in the Nicaragua case, of paramount importance in this area. This case arose out of forcible attempts by the USA to overthrow the socialist government in Nicaragua. The Court subsequently reaffirmed its commitment to this approach in 2005 in the Case Concerning Armed Activities on the Territory of Congo (DRC v Uganda). That is, there is a general consensus among states as to the principles to be applied to forcible intervention in civil conflicts, but in practice the disagreements as to the facts and as to the application of the law to those facts can fundamentally divide states, as can be seen clearly in the accusations and counter-accusations with regard to the current conflicts in Syria, Yemen, and Ukraine.

(p. 77) The Nicaragua Case

This case5 was brought by Nicaragua against the USA both for the unlawful use of force against the government of Nicaragua and for its intervention through its support for military and paramilitary activities of the opposition contra forces. The part of the judgment which deals with the use of force and non-intervention provides an authoritative statement of the law on this area; it has proved relatively uncontroversial among commentators, in contrast to the critical response from many US writers to the Court’s reasoning on collective self-defence.6 Indeed, there was consensus between the USA and Nicaragua as to the applicable law.7

Issues of classification played a central role in this case. Did the actions of the USA constitute an illegal use of force against Nicaragua under the customary international law rule codified in Article 2(4)? Were its actions an unlawful intervention against the government of Nicaragua? If so, could they be justified as collective self-defence or collective countermeasures in protection of Costa Rica, Honduras, and El Salvador against an armed attack or unlawful intervention by Nicaragua? The Court undertook an examination of the prohibition of intervention and of the scope of the prohibition of the use of force; it elaborated on the content of these two sets of rules and on the relationship between them. As regards the identification of the customary law on the prohibition of the use of force codified in Article 2(4), the Court used the Declaration on Friendly Relations principles on the use of force quoted at the start of this chapter on the duty not to organize civil strife in another state in support of an opposition party.8 It also set out the basic law on intervention at some length: ‘The principle of non-intervention involves the right of every sovereign state to conduct its affairs without outside interference; though examples of trespass against this principle are not infrequent, the Court considers that it is part and parcel of customary international law.’9 It invoked the Corfu Channel case, General Assembly resolutions, and inter-American practice as authority for the principle of non-intervention.

The Court then went on to consider the exact content of the principle as far as was relevant to the resolution of the dispute:

The principle forbids all states or groups of states to intervene directly or indirectly in internal or external affairs of other states. A prohibited intervention must accordingly be one bearing on matters in which each state is permitted, by the principle of state sovereignty, to decide freely. One of these is the choice of (p. 78) a political, economic, social and cultural system, and the formulation of foreign policy. Intervention is wrongful when it uses methods of coercion in regard to such choices, which must remain free ones. The element of coercion, which defines, and indeed forms the very essence of, prohibited intervention, is particularly obvious in the case of an intervention which uses force, whether in the direct form of military action, or in the indirect form of support for subversive or terrorist armed activities within another state. General Assembly resolution 2625 (XXV) equates assistance of this kind with the use of force by the assisting state when the acts committed in another state involve a threat or use of force. These forms of action are therefore wrongful in the light of both the principle of the non-use of force and that of non-intervention.10

After its statement of the general prohibition of forcible intervention the Court had to consider whether any fundamental modification of the principle of non-intervention had taken place. Significantly, the USA did not itself put forward any argument that there had been such a fundamental shift in the law. It did not advance the argument that it had a legal right to help the opposition contras to use force to overthrow a government; it based its right to use force on collective self-defence. Nevertheless, the Court examined the possible argument that the USA was justified in using force against Nicaragua to help the contras in their forcible opposition to the government. The ICJ said that a government may invite outside help, but a third state may not forcibly help the opposition to overthrow the government. Although there had been in recent years a number of instances of foreign intervention for the benefit of forces opposed to the government of another state, this did not in itself change the law. The Court had to consider whether there were indications of a practice illustrative of a belief in a kind of general right for states to intervene in support of internal opposition in another state, whose cause appeared particularly worthy by reason of the political and moral values with which it was identified. For such a general right to come into existence, a fundamental modification of the customary principle of non-intervention would be involved.

The Court, in considering whether there was opinio juris to support such a change, said it had to take account of the grounds offered by states to justify their interventions in support of opposition; states had not in fact justified their conduct by reference to a new right of intervention or a new exception to the principle of its prohibition. The US authorities had on some occasions stated their grounds for intervening in the affairs of a foreign state for reasons connected with the domestic policies of that country or its ideology, the level of its armaments, or the direction of its foreign policy. But these were statements of international policy and not an assertion of rules of existing international law. Accordingly, ‘The Court therefore finds that no such general right of intervention in support of an opposition within another State exists in contemporary international law. (p. 79) The Court concludes that acts constituting a breach of the customary principle of non-intervention will also, if they directly or indirectly involve the use of force, constitute a breach of the principle of non-use of force in international relations.’11 It later said that the principle of non-intervention would certainly lose its effectiveness as a principle of law if intervention ‘which is already allowable at the request of the government of a State’ were also to be allowed at the request of the opposition. This would permit any state to intervene at any moment in the internal affairs of another state.12

On the facts of the case the Court found that the US aid to the contras in Nicaragua in ‘recruiting, training, arming, equipping, financing, supplying and otherwise encouraging, supporting, aiding and directing military and paramilitary actions in and against Nicaragua’ was a breach of the prohibition of the use of force. The Court found that the USA had committed a prima facie violation of the principle of the non-use of force by ‘organizing or encouraging the organization of irregular forces or armed bands … for incursion into the territory of another state’ and ‘participating in acts of civil strife in another state’ in the terms of the Declaration on Friendly Relations. The arming and training of the contras could be said to involve the threat or use of force against Nicaragua, but the mere supply of funds to the contras, while undoubtedly an act of intervention in the internal affairs of Nicaragua, did not in itself amount to a use of force.13

The Court made it clear that it was not necessary to show that the intent behind the US intervention was actually to overthrow the government of Nicaragua. Nicaragua had claimed that this was the aim of the USA. But the Court said that in international law, if one state, with a view to the coercion of another state, supports and assists armed bands in that state whose purpose is to overthrow the government, that amounts to an intervention, whether or not the political objective of the state giving such support and assistance is equally far-reaching.14

Armed Activities on the Territory of the Congo (DRC v Uganda)

In 2005 the Court followed the Nicaragua case in its judgment on the case brought by the DRC against Uganda.15 The conflict which started in the vast, (p. 80) mineral-rich DRC (formerly Zaire) in 1998 serves as an example, though perhaps an unusually complex example, illustrating the type of conflict that has been common since the Second World War.16 After thirty-two years in power President Mobutu, supported by France throughout the Cold War, was overthrown by Laurent Kabila in May 1997 with the help of forces from some of the nine neighbouring states. Uganda and Rwanda helped Kabila to seize power partly because they were concerned to stop insurgents operating from the territory of the DRC challenging their governments. But when President Kabila came to power he himself used these insurgent forces and was seen as betraying his former allies; Uganda and Rwanda turned against him and undertook extensive military activities on the territory of the DRC against the government, against rebel groups, and even against each other.17 President Kabila sought help from Zimbabwe, Namibia, and Angola and they sent forces to support him in August 1998.18 Thus a civil conflict in the DRC was fuelled by outside involvement from many states because conflicts in their states had spilled over into the DRC and because the DRC had played a role in the conflicts in other states.19

The Security Council, in Resolution 1234 (1999), expressed its concern at reports of actions by forces opposing the government of President Kabila in violation of the national sovereignty and territorial integrity of the country; in the preamble it recalled the inherent right of individual or collective self-defence in accordance with Article 51 of the UN Charter. It also deplored the continuing fighting and the presence of foreign troops in a manner inconsistent with the principles of the Charter of the UN and called upon those states to bring to an end the presence of the uninvited forces. This resolution was based on the legal right of the government of the DRC to seek help and the illegality of the behaviour of the foreign states using force to overthrow that government. It showed that the Security Council took a clear position: aid to the government was permissible, intervention to overthrow the government was not.

After the Lusaka Ceasefire Agreement between the DRC and the five regional states involved in the conflict was concluded in July 1999 the Security Council’s main concern was to secure implementation of that Agreement and the deployment of a peacekeeping force, the United Nations Observer Mission in the Democratic (p. 81) Republic of Congo (MONUC).20 The DRC repeatedly wrote to the Security Council objecting that it was necessary to distinguish between the aggressor states—Uganda and Rwanda—and those aiding the legitimate government.21 Rwanda and Uganda continued to maintain that they had no territorial interests or economic interests in the DRC, but that they were concerned only to protect themselves against rebel forces operating from the DRC.22 However, the Expert Panel created by the Security Council to report on the ‘Illegal Exploitation of Natural Resources of the DRC’ reported that the armies of Uganda and Rwanda had carried out, first, mass-scale looting and then systematic exploitation of the DRC’s rich mineral resources.23

The Security Council distinguished between invited and uninvited forces again after the events of June 2000, when Ugandan and Rwandan forces fought over the diamond trade centred on the town of Kisangani—the first time since the Second World War that two foreign regular armies had engaged with each other in the territory of a third state with a view to appropriating that state’s wealth.24 The Security Council used unusually strong language in Resolution 1304 (2000). In the preamble it expressed its ‘outrage at renewed fighting between Ugandan and Rwandan forces in Kisangani’. It unreservedly condemned the fighting and expressly demanded that Uganda and Rwanda ‘which had violated the sovereignty and territorial integrity of the DRC’ withdraw their forces from its territory without delay, in conformity with the timetable of the Ceasefire agreement. In its subsequent resolutions, although it called for the withdrawal of all foreign forces, the Security Council continued expressly to single out Uganda and Rwanda.25 It did, however, also address the security concerns of Rwanda with regard to opposition forces operating from the DRC26 and condemn incursions into Rwanda and Burundi by armed bands from the DRC.27

(p. 82) After Laurent Kabila was assassinated in January 2001 he was succeeded as President by his son, Joseph Kabila, who was more willing to participate in the peace-making process.28 A final peace agreement was reached at the end of 2002 and a new government was installed.29 But the government found it difficult to assert control over its vast territory and fighting between armed militias continued, especially in the east of the country, despite the deployment of a large UN force in 2003. The DRC continued to accuse Rwanda of intervention, and the Security Council periodically expressed concern when Rwanda’s claims were supported by the Panel of Experts in its reports. Relations between the states of the region nevertheless improved and the signing of the Pact on Security, Stability and Development in the Great Lakes Region by eleven regional states on 15 December 2006 was an ‘historic development’ bringing hope for the future.30 This Pact includes a Protocol on Non-aggression and Mutual Defence in which the parties undertake ‘to abstain from sending or supporting armed opposition forces or armed groups or insurgents onto the territory of other states or from tolerating the presence on their territories of armed groups or insurgents engaged in armed conflicts or involved in acts of violence or subversion against the Government of another state’. However, the situation in eastern DRC remained violent and the government has continued to accuse Rwanda of illegal intervention.

The DRC in its Application accused Uganda of aggression, and of violation of the principle of unlawful use of force and also of ‘the principle of non-interference in matters within the domestic jurisdiction of states which includes refraining from extending any assistance to the parties to a civil war operating on the territory of another state’. Uganda admitted its assistance to an armed opposition group, the Movement for the Liberation of Congo (MLC), but claimed that this was limited to what was justified in self-defence.31 Like the USA in the Nicaragua case, Uganda did not claim a right to support armed opposition groups in their military campaign to overthrow a government, but rather a right to self-defence. It said that it was not acting unlawfully in supporting the armed opposition groups as it had refrained from providing the rebels with the kind or amount of support they would have required to achieve such far-reaching purposes as the conquest of territory or the overthrow of the Congolese government.32

The Court confirmed that the provisions of the 1970 Declaration on Friendly Relations on non-intervention were declaratory of customary international law.33 (p. 83) It held that Uganda’s actions were not justified self-defence,34 and since Uganda had admitted its training and military support for the MLC it was guilty of unlawful intervention. As in the Nicaragua case, Uganda could be held to have violated the prohibition on intervention even if its objective was not actually to overthrow President Kabila.35 ‘The Court accordingly concludes that Uganda has violated the sovereignty and also the territorial integrity of the DRC. Uganda’s actions equally constituted an interference in the internal affairs of the DRC and in the civil war there raging. The unlawful military intervention by Uganda was of such a magnitude and duration that the Court considers it to be a grave violation of the prohibition on the use of force expressed in Article 2, paragraph 4, of the Charter.’36

The Court considered another aspect of the law on intervention in regard to Uganda’s first Counterclaim against the DRC.37 Uganda claimed that the DRC had violated the principles of non-use of force and non-intervention because it had not only actively supported anti-Ugandan rebels operating from the DRC against the government of Uganda, but had also tolerated the activities of the rebels on its territory. This argument invokes a different aspect of the duty of non-intervention from that alleged by the DRC, and from that involved in the Nicaragua case. Uganda said that the duty of non-intervention involved not only the duty not to provide support to groups carrying out subversive or terrorist activities against another state, but also a ‘duty of vigilance’ to ensure that such activities were not tolerated. It argued that the DRC was guilty of intervention not only because of its active support for the anti-Ugandan rebels, but also because it had tolerated their activities on the territory of the DRC. According to the decision of the Court in the Corfu Channel case, every state had an obligation not to allow knowingly its territory to be used for acts contrary to the rights of other states.

The Court accepted that the prohibition of intervention as set out in the Declaration on Friendly Relations includes a ‘duty of vigilance’: the Declaration provides that ‘every State has the duty to refrain from … acquiescing in organized activities within its territory directed towards the commission of such acts’ (e.g., terrorist acts, acts of internal strife) and also that ‘no State shall … tolerate subversive, terrorist or armed activities directed towards the violent overthrow of the regime of another State’. However, Uganda failed to prove its allegations of intervention. It did not show active support by the DRC for attacks on Ugandan territory.38 Nor did it show acquiescence or toleration of anti-Ugandan rebels on its territory. The parties did not dispute the presence (p. 84) of the rebels on the territory of the DRC. Uganda argued that before 1997 the rebel groups were able to act unimpeded in the border region because of its mountainous terrain, its remoteness from the capital, and the almost complete absence of central governmental presence in the region. The Court did not accept that the absence of action by the government of the DRC (then known as Zaire) against the rebel groups in the border area was tantamount to ‘tolerating’ or ‘acquiescing’ in their activities.39 At first the DRC had not been capable of stopping the actions of the rebels; subsequently it had in fact taken clear action.40 This is an important decision on the scope of the duty of non-intervention. The Court took a strict approach and was not willing to accept that inability to act against rebels or ineffective action make a state guilty of intervention. There must be actual toleration or acquiescence. Clearly this may be difficult to prove. Hence the dissenting judges in this case argued it was for the state accused of unlawful intervention to show that it had discharged its ‘duty of vigilance’, but the Court did not agree.41

The Right of a Government to Invite Outside Intervention

The reference by the Court in the Nicaragua case to the legality of intervention in response to an invitation by the government was very brief; this brevity masks the complexity that may arise in the interpretation and application of this rule. The basic principle of the right of a government to invite a third state to use force and the absence of any such right for an opposition may be accepted in theory, but its application in practice has not been simple.42 Chapter 2 examined the debates as to humanitarian intervention, national liberation movements, and pro-democratic intervention; the law on all these may affect the legality of help to the opposition in a state. Various other limits on the right of a government to seek and receive outside assistance have been suggested as evolving through practice since the inception of the UN. Commentators have given increasing attention to this question in response to the conflicts in Iraq (2014), Syria (2011), Ukraine (2014), Yemen (2015), and Mali (2013).

(p. 85) The UK set out the generally accepted position during the Cold War in a Foreign Policy Document in 1984. This expounded the general prohibition of forcible intervention and the possible exceptions to this.43 It said that normally if one state requested assistance from another, then clearly that intervention could not be dictatorial and therefore unlawful. But a major restriction on the lawfulness of states providing outside assistance to other states was that any form of interference or assistance was prohibited when a civil war was taking place and control of the state’s territory was divided between warring parties.44

Classification of conflicts

According to this view, the categorization of a conflict may therefore be crucial in the determination of the legality of forcible intervention. The question arises first as to whether a conflict is actually a civil war or whether it is merely limited local unrest. Are opposition forces in control of territory? This line between unrest and civil war has proved controversial. States have not on the whole been willing to admit that the threshold of a civil war has been reached; they see such an acknowledgement as legitimating opposition forces. This has proved a fundamental obstacle to the effective implementation of humanitarian law in non-international armed conflicts. Second, if the conflict is a civil war, is it a purely civil war or has there been outside intervention? What has been the scope of the outside intervention: does it amount to an armed attack allowing collective self-defence or is it merely a lesser intervention allowing aid short of collective self-defence to the government? Is the government using force against a people with the right of self-determination? All these issues affect the rights of third states to intervene to assist the government.

Even the determination as to whether a conflict is an inter-state conflict or a civil war may be far from straightforward. Questions as to classification—is the conflict civil or international?—may be decisive as to the applicable law and as to the legality of the use of force. In the past this issue came up dramatically over the 1961–75 war in Vietnam. The competing parties fundamentally disagreed as (p. 86) to the nature of the conflict. The USA and South Vietnam argued that the conflict was an inter-state war begun by the invasion of South Vietnam by North Vietnam, a Cold War conflict in which the USA was operating in collective self-defence of its ally against a Chinese-aided invasion by North Vietnam. North Vietnam argued that the conflict was one of decolonization; the people of the whole of Vietnam were resisting the perpetuation of colonial rule.45 If the former was accurate, then the rules applicable were those in Article 51 on inter-state conflict; if the latter view was correct, then the conflict was one in which the USA was intervening in a struggle for decolonization by the people of the whole of Vietnam. The Security Council did not play an active role in this conflict and did not pronounce on the issue.46 Conflicts in other divided states such as Korea, Yemen, and Ireland have given rise to similar issues of classification.

The question of classification also came up in the 1991–5 conflict in Bosnia-Herzegovina.47 The states involved took radically opposing views on the nature of the conflict; Bosnia-Herzegovina said that it was the victim of aggression by Yugoslavia (Serbia and Montenegro) whereas Yugoslavia claimed that the conflict in Bosnia was a civil war. This issue of classification arose in many different contexts; it was central to the case brought by Bosnia against Yugoslavia before the ICJ; it affected Yugoslavia’s claim to be treated as the successor state to the former Yugoslavia; it was important in the debate over the lifting of the arms embargo on Bosnia and on Bosnia’s right to self-defence. The issue of classification was also central to the application of the laws of war.48

Invitation by governments in practice

However, commentators are divided as to whether the UK position on the prohibition of intervention in civil wars is still—if it ever was—the law. Is there a rule of ‘negative equality’, a rule against intervention to assist the government during a civil war, just as there is undoubtedly a rule against intervention to assist (p. 87) an armed opposition.49 If there was such a rule against intervention on the side of a government during the Cold War, there were many ways round it in practice. More recent practice does not show express assertions by states of a rule against intervention on the side of a government during a civil war; it does show states sometimes invoking self-defence against terrorism, or assistance to a government against terrorism, to justify their military intervention in an internal conflict. The continuation of the US counter-terrorism operation in Afghanistan after the termination of Operation Enduring Freedom at the end of 2014 rests on consent by the government.50 The French intervention in Mali—Operation Serval—was justified on the same basis: it was acting to help the government against Al Qaida in the Islamic Maghreb.51 This type of justification enabled France to avoid accusations of neo-colonial interference.

The 2014 intervention in Iraq by the US-led ‘Coalition against ISIL’ at the request of the government was to help it against the serious threat from ISIS.52 The Iraqi army had collapsed in the face of ISIS’s dramatic advances and seizure of territory. Iraq requested Iran to provide military assistance.53 It also asked the USA to lead international efforts to strike ISIS sites, and states including Australia, Belgium, Canada, Denmark, France, Jordan, Netherlands, and the UK joined in the military operations in Iraq (Operation Inherent Resolve).54

It is striking that the UK’s summary of its legal position affirmed in absolute terms that the prohibition on the use of force ‘does not apply to the use of military force by one state on the territory of another if the territorial State so requests or consents’.55 The legality of this intervention in Iraq itself was not challenged (p. 88) by other states, in contrast to the mixed response to the extension of these operations against ISIS to Syria, also claimed to be at the request of the government of Iraq.56

More controversially, when the USA carried out air strikes in Somalia and Yemen it claimed that it was acting in self-defence as part of its war on Al Qaida and its affiliates, Al Qaida in the Arabian Peninsula (AQAP) and AlShabaab.57 But the escalation of air strikes, many by drones, and the increase in US troops on the ground in those states under President Trump has reopened the question as to the nature of the military intervention. It is not always possible to draw a clear line between action against alleged terrorists in self-defence, and intervention in a civil war by killing those identified by the government as terrorists. The surge in US attacks in 2017 raised the question whether the USA had gone beyond targeted killing of those alleged terrorists who threaten an imminent attack on the USA (identified as ‘external planners’) and was now attacking those that posed a threat to the governments of Yemen and Somalia, and to the US special forces on the ground giving assistance to those governments.58

Thus, the characterization of opposing forces as terrorists may be problematic. Soon after the terrorist attacks of 9/11, the UN Secretary-General expressed concern that states were increasingly using the ‘T word’—terrorism—to demonize political opponents and to de-legitimize legitimate political grievances. ‘States fighting various forms of unrest or insurgency are finding it tempting to abandon the sometimes slow process of political negotiation for the deceptively easy option of military action.’59 In Syria there was a fundamental division on this question of classification. After protests against the Assad government (as part of the 2011 ‘Arab Spring’) met with violent repression, some of the protestors turned to armed opposition and the Assad government claimed that the opposing forces were terrorists.60 It invited Russia and Iran to provide assistance.61 However, the Security Council did not address the threat posed by terrorists in Syria until quite (p. 89) late in the conflict.62 Other states, including Turkey, categorized the conflict as a pro-democratic uprising.63 The USA, Saudi Arabia, and other states intervening on the side of the opposition have tried to distinguish between terrorists and ‘moderate opposition’ forces in their provision of support.64

In Libya, the state descended into civil war in the aftermath of the 2011 NATO-led military intervention and the overthrow of Colonel Gaddafi,65 and ISIS was able to seize territory here as well as in Iraq and Syria. In 2015 the Security Council called on states to combat ISIS and other terrorist groups in coordination with the government of Libya.66 Security Council Resolution 2259 (2015) ‘urges Member States to swiftly assist the Government of National Accord in responding to threats to Libyan security and to actively support the new government in defeating ISIL’ and other groups operating in Libya ‘upon its request’. The USA responded to requests by the Government of National Accord and initiated Operation Odyssey Lightning which carried out 495 air strikes (1 August–19 December 2016) to drive ISIS out of the town of Sirte. This was justified by the USA on the basis that it was acting ‘at the request of and in coordination with’ the Libyan government, to deny ISIS a safe haven from which to attack the USA and its allies.67 The USA resumed its air strikes against ISIS in Libya in September 2017. The situation remains volatile.68

But what is not clear is whether this explanation was adopted by the USA simply for political reasons—or for reasons to do with domestic constitutional constraints on the use of force.69 Just because states do not acknowledge that they are intervening in a civil war, and because they seek to explain their actions on the basis of their purpose (fighting terrorism), this does not necessarily mean (p. 90) that they accept that intervention in civil war at the request of a government is forbidden.70

Many states have relied on an invitation by a government to justify their use of force; they have avoided possible accusations of intervention in a civil war by claiming that their intervention was lawful because they were merely dealing with limited internal unrest or, at the other end of the spectrum, because they were helping the government respond to prior intervention by other states. In many cases a government has been maintained in power not by the actual use of force by foreign troops, but by less dramatic means. A foreign government may provide financial support or arms or training for the armed forces or police. Foreign military bases or other forms of foreign military presence may also provide stability.71 During the Cold War the superpowers and other states used these means to help maintain friendly governments in power. US support for the governments that it helped to install by coups in Guatemala (1954), Chile (1973), and Iran (1953) and for pro-Western governments all over the world, and USSR support for governments such as those of Cuba, Angola, Vietnam, and Ethiopia was well known. Similarly France supported certain regimes in Africa in order to maintain its influence; it concluded defence treaties and retained bases in many of its former colonies. Also its support for rulers in francophone Africa such as President Mobutu in Zaire, Emperor Bokassa in the CAR, the Hutu regime in Rwanda, and President Eyadema in Togo helped them to remain in power for many years.72 In recent years it has employed (and augmented) French troops already present in the state to carry out military operations in support of the democratically elected government in Côte d’Ivoire, of the UN-supported transitional government in Mali in its counter-terrorism operations, and of the transitional government in the CAR to restore order.73 It maintains troops in Chad as part of Operation Barkhane, a regional anti-terrorism force, and has other military bases in Djibouti, Senegal, and Gabon. The USA bases its African command, AFRICOM, in Djibouti and maintains several other lower profile outposts. China has established its first military base in Africa in Djibouti.

The right of a third state actually to use force at the invitation of a government in order to keep that government in power or to maintain domestic order has (p. 91) apparently been taken for granted by states since 1945 if the domestic unrest falls below the threshold of civil war. The case of Sri Lanka (1987–90) demonstrates the reluctance of states to acknowledge the existence of a civil war; states may continue to claim that a conflict is mere internal unrest even when rebels have in fact gained control of territory.74 The Tamil Tigers sought a separate state for the minority Tamil population; the government of Sri Lanka regarded the Tamil Tigers as a terrorist force without legitimacy. India, which has a large Tamil population in Tamil Nadu, and which was accused of allowing support to the Tamil Tigers from its territory, put pressure on Sri Lanka to negotiate a political settlement with the Tamil Tigers. But in 1987 Sri Lankan government troops responded to the increasing attacks by the Tamil Tigers by resorting to large-scale force against them; the government attempted to reassert control of the Jaffna peninsula from which the Tigers operated and which they effectively controlled. India then intervened. It sent humanitarian supplies to Sri Lanka destined for the Tamils; the ships carrying this were turned back by the Sri Lankan navy. India then made airdrops over Sri Lanka; Sri Lanka protested.75 Under pressure from India the government of Sri Lanka entered into negotiations with the Tamil Tigers and with India and arranged a far-reaching ceasefire agreement. This agreement included a provision that Sri Lanka could request India to send troops to police the ceasefire.76 Sri Lanka immediately made such a request.

Both states insisted on the legality of the Indian presence. Sri Lanka said that India was there at its invitation and would leave when requested.77 The ceasefire agreement broke down and India sent a total of 65,000 troops to try to stop the disorder; they operated against the Tamil Tigers in the north. Just as there was room for doubt about the free nature of the original invitation to India to intervene, so the voluntary nature of the continuation of that consent was also doubtful. India proved reluctant to withdraw its troops even when asked to do so by Sri Lanka in June 1989. The Indian forces finally left in March 1990. The Indian intervention did not meet with any UN response.

Another example of a state denying intervention in a civil war can be seen in the US insistence that it was not interfering in the long-running (since the 1960s) civil war in Colombia but was merely helping the government to fight the drugs trade. The USA funded and trained a Colombian anti-narcotics army battalion and shared intelligence with the Colombian army, but denied any intent to intervene militarily in the conflict. The theoretical distinction that the USA drew between the anti-drugs efforts and involvement in the civil war was difficult to maintain in practice.78 The USA later justified its continuing large-scale (p. 92) assistance to the government as part of the unified war against narcotics and terrorism.79 The Colombian conflict between the government and the FARC rebels was finally brought to an end by a peace agreement in 2016.80

It is commonly said that the Definition of Aggression implicitly acknowledges the right of a state to invite a foreign army because it spells out that failure of that foreign army to leave or actions in excess of the invitation will constitute aggression.81 Interventions limited to action to help governments to repress local protests or army mutinies attracted relatively little international attention during the Cold War. There were many instances of such intervention at the request of the government by former colonial powers, France and the UK, ostensibly to help the restoration of order.82 In 2011 the government of Bahrain when faced with protests similar to those in other states in the region during the Arab Spring called in troops from Saudi Arabia and other members of the Gulf Cooperation Council (GCC) to keep the Sunni rulers in power in a Shiite majority state. There was little international response to the intervention.83 Iran expressed concern at the repression of the peaceful protests; it said that the big powers had chosen to stand aside, and asked whether this indicated that good allies may always have greater scope in terms of violence.84 It seems that there was no challenge by states to the right of the government to invite intervention, but an invitation cannot justify unlawful action in violation of human rights or international humanitarian law by the intervening state.

In contrast to the above examples of intervention which have escaped international condemnation, there have been dramatic abuses of the right to assist a government. The USSR intervention in Hungary in 1956 to repress the move away from one-party rule was justified by the USSR as a response to a request from the former Prime Minister. It was ‘an internal matter’ for Hungary to invite the Soviet forces already present in Hungary to suppress an armed rebellion by a (p. 93) ‘reactionary underground movement’. This intervention was condemned by the General Assembly by 50–8–15, and condemnation by the Security Council was avoided only by a USSR veto.85 It is striking that when the USSR later intervened in Czechoslovakia in 1968 to deal with a similar attempt to move away from one-party rule it did not again base its justification on an invitation to deal with internal unrest; rather, it sought to portray the events in Czechoslovakia as an international conflict. The move for change in Czechoslovakia was portrayed as the result of foreign subversion which justified intervention to assist the government.86

The maintenance of order was also one of the justifications that was claimed by Iraq for its invasion of Kuwait in August 1990; it said that its forces had responded to a request from the Free Provisional Government of Kuwait to assist it ‘to establish security and order so that Kuwaitis would not have to suffer’. Iraqi troops would withdraw as soon as order had been restored.87 This specious claim was unanimously rejected by the Security Council in Resolution 660 (1990) which condemned the invasion and called for the immediate and unconditional withdrawal of Iraqi forces. In both these cases claims to be using force to help a government maintain order were mere pretexts for much more far-reaching intervention and as such were rejected by the Security Council in the case of Kuwait and by the General Assembly in the case of Hungary.

Because intervention to prop up unpopular governments has often proved controversial, foreign states in some instances have not openly said that they were using force to quell unrest at the request of the government. Rather, they have chosen to say that their role was limited to the protection of their nationals with the consent of the government, or to claim this as an additional justification to strengthen the other.88 One well-known example is the intervention in Congo in 1964. US and Belgian forces went into Congo (as it then was) at the request of President Tshombe, who was faced with rebel seizure of Stanleyville; they reported to the Security Council that they had been invited by the government and were also acting to protect US nationals. Twenty-two states called for a meeting of the Security Council and condemned the intervention; they said that the intervention was a dangerous precedent which might threaten the independence of African states. They also questioned the legality of the government. The USSR claimed that President Tshombe had not taken the initiative of requesting the Stanleyville operation, but had rather given his agreement only after such an agreement had been sought from him. The Congo in turn accused China, (p. 94) the USSR, and other states of assisting the rebels. The Security Council passed Resolution 199 in general terms requesting all states to refrain from intervention and appealing for a ceasefire.89

This type of justification for intervention can be seen also in the UK intervention in Sierra Leone in 2000. This was initially claimed to be an action undertaken to allow its nationals to leave the country, but it was clear that there was also an intention to prop up the government against rebel forces at a critical time. The UK forces took action to secure the airport and the capital against rebel forces.90 In September 2000 the UK said that British troops were in Sierra Leone for three reasons: to protect the people, to assist the democratically elected government, and to provide support to the UN peacekeeping force.91 The UK subsequently offered training and equipment to the Sierra Leone army and helped to fund the disarmament of the rebel forces.92

More attention has been paid to the instances when the USA used force claiming to be acting both at the invitation of a government and in protection of nationals. The USA, in its forcible interventions in the Dominican Republic (1965) and Grenada (1983), used the justification that it was invited by the legitimate government as part of a regional peacekeeping operation and also that it was acting to protect US nationals in self-defence; in both operations it actually overthrew the old government and installed new governments. Controversy about the existence of the invitation and its constitutional propriety was strong in both cases; in the former the invitation came from unspecified ‘government officials’ and in the latter from the Governor-General, a post without executive powers. The intervention in the Dominican Republic was the first overt military intervention by the USA after the Second World War, designed to prevent the establishment of another communist government in the Western hemisphere; its legality was supported in the Security Council only by the UK. There was also criticism in the General Assembly, but no condemnation by either body.93 The intervention in Grenada was condemned by the UN General Assembly which said it ‘deeply deplores the armed intervention in Grenada, which constitutes a flagrant (p. 95) violation of international law and of the independence, sovereignty and territorial integrity of that state’.94

It is significant that when the USA intervened in Panama in 1989 it chose not to rely on invitation by a government. Although it noted that Guillermo Endara (who had a clear claim to the presidency because he had been elected to replace General Noriega, but had been prevented by him from taking power95) had welcomed the intervention, the US legal justification as reported to the Security Council was self-defence in protection of its nationals and defence of the Panama Canal under the 1977 Canal Treaty. This reluctance to rely on invitation may indicate a new caution about using invitation by a ‘legitimate’ rather than an effective government. The Security Council resolution denouncing the US intervention was vetoed by the USA, the UK, and France on the ground that it was unbalanced in that it did not address the illegal nature of the Noriega regime. The General Assembly condemned the intervention in Resolution 44/240 by 75–20–40. This less than overwhelming vote is usually explained as attributable to the hostility to Noriega and the special relation of the USA to Panama. The OAS, however, overwhelmingly condemned the intervention.96

In all these cases of US intervention the defence of nationals was used to mask the use of force to overthrow the government; the motive of the USA was to install a new government more ideologically appealing to it. The claim of invitation was controversial in the case of the Dominican Republic, was not accepted as a justification in the case of Grenada, and was abandoned in Panama. The US interventions clearly went beyond the protection of nationals that was claimed as one of the justifications for the intervention and the invitation was not enough to legitimate the intervention as far as a majority of states were concerned.97

Intervention in Response to Prior Foreign Intervention

Even if there is a civil war, states have justified forcible intervention at the request of the government on the ground that there has been prior foreign intervention against the government. During the Cold War this was a well-established exception to any prohibition of intervention in civil wars, but one of the most abused. (p. 96) The USSR interventions in Czechoslovakia (1968) and Afghanistan (1979) are the most infamous examples of abuse of the doctrine that prior foreign intervention justifies counter-intervention at the request of the government.98 In both the invitation was a fiction. In the former the USSR first claimed invitation by the existing government, but Czechoslovakia appeared before the Security Council to deny this.99 In Afghanistan the USSR installed a new government and then said that it had invited in their forces.

The intervention in Czechoslovakia was explained by the USSR in terms of the ‘Brezhnev doctrine’ of limited sovereignty for socialist bloc states: this portrayed the movement away from one-party socialism in Czechoslovakia as necessarily the result of foreign subversion and thus as justifying a forcible response by the USSR in collective self-defence.100 Inconsistently with this, the USSR also argued that the matter was a purely internal affair for Czechoslovakia and so not appropriate for discussion in the Security Council.101 Under President Gorbachev the USSR later expressly disavowed the Brezhnev doctrine; the USSR and the four other Warsaw Pact states which had participated in the invasion and occupation made a statement condemning the invasion of Czechoslovakia as an unlawful interference in an internal dispute and an intervention in a friendly state. They also acknowledged that the intervention in Hungary had been unjustified.102 The 75,000 Soviet troops remaining in Czechoslovakia were withdrawn by May 1991. The USSR and Czechoslovakia, and later Russia and Czechoslovakia, concluded Friendship Treaties confirming the denunciation of the 1968 invasion.103

In Afghanistan the new government installed by the USSR said that it had requested Soviet military aid because of foreign threats. The USSR claimed that it was responding to a request from the government to repel armed intervention from outside on the basis of a treaty of December 1978. In the Security Council debate the USSR said that it was responding to US and other Western intervention and China’s intervention in Afghanistan’s internal affairs to foment counter-revolution; in the General Assembly it invoked instead collective self-defence.104 This intervention, unlike that in Czechoslovakia, was condemned by a resolution (p. 97) of the General Assembly.105 The Soviet forces remained until 1989.106 In both these cases, Czechoslovakia and Afghanistan, the claim of an invitation masked an invasion to overthrow the government.

Turkey also invoked a prior intervention to justify its invasion of Cyprus in 1974 and again this justification was overwhelmingly rejected by the UN. In July 1974 a coup was instigated against the President of Cyprus, apparently with the support of the government of Greece, in order to destroy the constitution created for Cyprus on independence and to secure the union of Greece and Cyprus. The constitution had been designed to protect the interests of both Greek Cypriot and Turkish Cypriot communities. Turkey argued that this was equivalent to a Greek intervention in Cyprus and therefore that it was justified in using force under the 1960 Treaty of Guarantee to secure the independence and constitution of Cyprus. Article IV provided that, ‘In the event of a breach of the provisions of the present Treaty, Greece, Turkey and the United Kingdom undertake to consult together with respect to the representations or measures necessary to ensure observance of those provisions. Insofar as common or concerted action may not prove possible, each of the three guaranteeing powers reserves the right to take action with the sole aim of reestablishing the state of affairs created by the present Treaty.’ Turkey seized control of about a third of Cyprus and in 1983 Turkish Cyprus proclaimed itself a state.107

The Security Council passed a series of resolutions at first deeply deploring the outbreak of violence and calling for a ceasefire and an immediate end to foreign military intervention in Cyprus; Resolution 360 (1974) expressed formal disapproval of the unilateral military actions against Cyprus and the withdrawal of foreign military personnel.108 The General Assembly also condemned the intervention in Resolution 3213 (1974) by 117–0. The Turkish use of the Treaty of Guarantee was apparently not accepted as justifying unilateral forcible intervention, although there was no extended discussion of this in 1974.

Other states making forcible interventions in civil wars during the Cold War almost invariably argued that they did so in response to a prior outside intervention against the government.109 France repeatedly justified its interventions in African states by claiming that it was responding to prior foreign intervention. For example, it used force to help the government of Tunisia in 1980, saying that (p. 98) it was threatened by insurgents supported by Libya.110 In 1986 it helped Togo to keep the dictator Eyadema in power, saying that Ghana and Burkina Faso had intervened against the government.111 It helped the government of Djibouti in 1991 against an alleged Ethiopian intervention; the defence treaty between France and Djibouti did not allow intervention to restore domestic order but did allow the use of force if there was a foreign threat.112 Other states have also used this justification. Senegal helped the government of Gambia against alleged Libyan opposition in 1981 under their 1965 mutual defence agreement.113 From 1986 Tanzania and Zimbabwe used force to help the government of Mozambique in its battle against subversion by South African-backed RENAMO rebels.114

Those rejecting these claims denied the existence of such prior intervention, or denied that there was any invitation from the government. Intervention in response to government request has met with protest when it was seen as support for an unacceptable government or for an outdated monarchy. In the 1950s and 1960s the UK in the Middle East claimed to be responding to government requests by Jordan, Oman, and North Yemen to deal with outside subversion or even threatened armed attacks, but it encountered criticism that it was hiding its true motives. The Security Council in these cases was called on to take a view as to whether an intervention was a lawful response to an invitation by a ruler to an outside threat, even amounting to collective self-defence, or whether it was an interference with a popular movement to overthrow a hereditary ruler, an attempt to keep in power a ruler sympathetic to a former colonial power.115 As with the USA in Vietnam, the UK description of its role as support at the invitation of a government to resist outside subversion or attack was rejected by others who saw it as the perpetuation of colonial rule.

The problems with the application of the doctrine that a government may invite outside intervention in a civil war if there has been foreign interference were also apparent in the 1975–93 civil war in Chad. Thus when France and Libya intervened in the prolonged civil war each supported a different faction and claimed that it was the true government of Chad.116 The complexities of the long civil war in which leaders repeatedly shifted allegiance made any objective assessment of the validity of these claims problematic. France maintained a military presence (p. 99) in Chad almost continuously from its independence in 1960; the French position when it actually used force was that it was helping the government against Libyan intervention or sometimes that it was acting in collective self-defence of Chad against Libya. Libya generally denied intervention; it said that the conflict in Chad was internal. It also denied the legitimacy of the government which had invited France. When a pro-Libyan government came to power in Chad in 1979 the positions were reversed and Libya claimed invitation by the government in response to prior foreign intervention.117 Thus the states involved agreed on the applicable rules on intervention, but disagreed fundamentally on which was the legitimate government and on the characterization of the conflict. The same pattern could be seen in Angola and Mozambique.118 Since 2001 it seems that states have more often claimed that they are acting to assist a government against terrorists than that they are acting in response to prior foreign intervention. But there were signs of the latter doctrine in the conflict in Yemen.119

During the ‘Arab Spring’ of 2011 there were serious protests against President Saleh of Yemen who had been in power since 1978.120 He was persuaded to stand down and a successor, Hadi, came to power through an uncontested election in 2012. However, there had been tensions in Yemen ever since the unification of North and South Yemen in 1990; separatist groups in the south, Houthi rebels in the north, and Al Qaida in the Arabian Peninsula all challenged the power of the government. In 2014 Houthi rebels made major advances and took the capital of Yemen, and President Hadi fled, first to the south of Yemen and then to Saudi Arabia. In 2015 President Hadi wrote to the Security Council seeking help from the Gulf Cooperation Council, and it began Operation Decisive Storm, led by Saudi Arabia. This military operation was to continue for over two years, and the air and ground campaign and naval blockade caused massive devastation in Yemen, already the poorest Arab state, but one of great strategic significance because of its proximity to major shipping routes.

At first there was some confusion about the legal basis for the intervention: President Hadi’s letter to the Security Council referred not only to an invitation to the GCC to intervene, but also to self-defence against aggression supported by an unspecified ‘regional power’ whose object was to dominate the country.121 This was generally taken to mean (Shia) Iran, (Sunni) Saudi Arabia’s regional rival. The invocation of self-defence was implausible, given the absence of any armed attack on Yemen.122 But President Hadi continued to make accusations (p. 100) of Iranian intervention on the side of the Houthis.123 Other GCC states and the USA repeated these accusations, but they did not produce any evidence to back up these claims,124 and the accusations were not accepted by the Yemen Panel of Experts set up by the Security Council.125 There was no challenge to the legality of the Saudi-led intervention, except by Iran.126 Criticism of the campaign focused on violations of international humanitarian law and on the terrible impact on the population of Yemen. In 2017 the Panel of Experts found that after nearly two years of conflict, an outright military victory by one side was not a realistic possibility; the air campaign while devastating to Yemeni infrastructure and civilians had failed to dent the political will of the Houthis to continue the conflict. And during the conflict terrorist groups such as AQAP and ISIS (which now appeared in Yemen for the first time) were exploiting the political environment to recruit new members and stage new attacks.127

The Identification of the Government Entitled to Invite Intervention

It is apparent that in many of these cases there has been controversy as to the right of the government to invite outside intervention. This question as to who may invite outside help arises not only in this context of civil wars but also with regard to collective self-defence, invitation to UN and regional peacekeeping forces, and rescue of foreign nationals. Academic debates about the effectiveness and legitimacy of governments have been common; writers have divided on the question whether an invitation can justify intervention only if it comes from the effective government or whether it is the legitimate government that has the right to invite assistance to maintain itself in power or to restore it to power when it has been overthrown. Such academic debate has been inconclusive in the light of the diversity of state practice. Roth’s exhaustive 1998 study demonstrated persuasively that state practice had not produced uniform doctrine as to who counts as the government with the right to invite outside intervention in this context. Cold War divisions meant that, although there was agreement as to the principles governing non-intervention, states often divided on political lines in their determination of who was the government or whether there was a government, whether there actually was an invitation and, if so, whether it was freely given.128 The (p. 101) disagreements as to who was the government in Chad and Angola are among the most dramatic examples of splits along Cold War lines; the question also arose with regard to Hungary, Afghanistan, Czechoslovakia, the Dominican Republic, and Grenada. In all these cases the claims of invitation were not accepted as a justification for the use of force and the intervention led to condemnation. But in Security Council and General Assembly debates on the use of force, although there has been discussion of the reality of the invitation and of the effectiveness or legitimacy of the government concerned, the main focus has been on the substantive issue of whether the invitation was a mere pretext for intervention.129

The prolonged Syrian intervention in Lebanon from 1976 to 2005 escaped condemnation for many years.130 Syria kept a substantial number of troops in Lebanon for almost thirty years after 1976; it maintained that it had a special ‘fraternal’ relation with Lebanon, deriving from their early unity under the Ottoman Empire until the territory was divided by France during the mandate.131 In 1975 civil war broke out in Lebanon between the Maronite Christians on one side and the Muslims and Palestinians on the other.132 Israel secretly supplied weapons to the Christians133 and Syria sent troops to Lebanon, at the invitation of the President.134 Israel and the USA initially acquiesced in the Syrian intervention; Iraq and Libya protested. But in June 1976 the Syrian intervention acquired greater legitimacy through its official absorption into an Arab League regional peacekeeping force of about 30,000 soldiers. This remained in Lebanon until 1983, and was dominated by the Syrians. From 1979 this force was intermittently involved in clashes with Israeli forces in Lebanon. Israel had invaded Lebanon in 1978 in response to a terrorist attack (for which Lebanon denied responsibility); the Security Council in Resolution 425 (1978) called on Israel to withdraw and also called for a strict respect for the territorial integrity, sovereignty and political independence of Lebanon.135 In contrast the legality of Syria’s presence was not challenged in the UN.

After 1982 the situation changed and the USA and Israel took a different line with regard to the Syrian presence in Lebanon. Israel carried out a major invasion of Lebanon in 1982 in response to minor border incidents and to a terrorist attack (p. 102) on the Israeli ambassador to the UK; it subsequently carried out a prolonged siege of Beirut.136 The Security Council again called on Israel to withdraw its forces in Resolution 520 (1982), but Israel continued to occupy southern Lebanon until 2000. From 1984 (after the peace treaty negotiated in May 1983 between Israel and Lebanon was rejected by Lebanon) Israel and the USA protested at the Syrian presence. They complained of double standards in Security Council debates on Israel and the Lebanon; they said that, in contrast to the repeated calls for Israeli troops to leave the ‘security zone’ that they occupied in south Lebanon, little had been said by other states about the presence of 50,000 Syrian troops in Lebanon.137 The USA vetoed resolutions calling for Israeli withdrawal, saying that it was necessary that all foreign forces should leave. Syria replied that its presence was based on a legitimate Lebanese request: Israel tried to give the impression that the Syrian presence was an occupation imposed on Lebanon, but in fact it was there at the request of the legitimate Lebanon government. The Arab League said that whatever might have been the circumstances of the Syrian presence it could not be equated with that of Israel.138 In December 1985 the position was formalized in the 1985 Damascus Accord; Lebanon and Syria both referred to this as an invitation justifying the continued Syrian presence. Israel challenged this, saying that the agreement simply formalized Syrian control of Lebanon.139 That is, there were occasions when the Syrian presence in Lebanon was challenged, but on the whole it was only Israel and the USA which did so without support from other states.

However, the situation changed after 9/11, and especially after Operation Iraqi Freedom in 2003. The USA increasingly accused Syria of support for terrorism against Israel and against Iraq; it began a campaign to secure the withdrawal of Syria’s troops from Lebanon. Thus, for example, in December 2003 the USA passed the Syria Accountability and Lebanese Sovereignty Restoration Act. This proclaimed that Syria was a ‘state sponsor of terror’ responsible for support for international terrorism by its provision of safe haven for organizations such as Hezbollah and various Palestinian groups including Hamas. Syria exerted undue influence on Lebanon, through the presence of its 20,000 troops; it was preventing Lebanon from complying with the requirement of Security Council Resolution 425 (1978) to deploy its troops to the southern border, and it was allowing Hezbollah to operate against Israel from southern Lebanon. The Act (p. 103) also accused Syria of pursuing WMD, and of allowing the transfer of weapons to insurgents in Iraq. Therefore, the Act demanded that Syria should inter alia immediately halt support for terrorism, and announce its commitment completely to withdraw its armed forces from Lebanon. It imposed sweeping sanctions on Syria until it should comply with these demands.

In 2004 there was a major change in the approach of the Security Council with regard to the Syrian presence in Lebanon. The Security Council passed Resolution 1559 (2004) by 9–0–6 (Algeria, Brazil, China, Pakistan, Philippines, and Russia) to bring an end to the Syrian military presence in Lebanon. This was an extremely controversial resolution; it was not passed under Chapter VII of the UN Charter. It seemed that a majority in the Security Council was no longer willing to take at face value the argument that the Syrian troops were lawfully in Lebanon with the consent of the government.140 However, Lebanon itself spoke in opposition to the consideration of the resolution and called for its withdrawal: ‘Friendly Syria had helped Lebanon to maintain stability and security within its borders. It has fended off the radicalism and violence that are fed by Israel’s extremism and violence against the Palestinians.’ Syrian troops came to Lebanon in accordance with legitimate requests. There were no militias in Lebanon, but only the Lebanese national resistance which would remain as long as Israel occupied parts of Lebanon. Syria supported this Lebanese national resistance.

International pressure grew after February 2005; the catalyst for revolutionary change in Lebanon was the assassination of former Prime Minister Rafik Hariri on 14 February 2005.141 Suspicion fell on Syria and the pressure on it mounted.142 It finally agreed to withdraw its troops and completed this process by the end of April 2005.143 However, there were problems with regard to Hezbollah, and with the extension of the control of the government of Lebanon over all its territory. The Security Council accordingly called for the full implementation of Resolution 1559 in a series of resolutions.144 Lebanon’s position on Hezbollah was that it was not a militia but a national resistance group with the goal of defending Lebanon from Israel, and the removal of Israeli forces from Lebanon. It had first been established in response to Israel’s occupation of Lebanon in 1982. Lebanon now claimed that its concern was to recover the Shab’a farms from Israeli occupation.145 But the border which had been established by the UN at the time of the withdrawal by Israel in 2000—the Blue Line—put the Shab’a farms on the (p. 104) Israeli side of the border, treating it as Israeli-occupied Syrian territory.146 This was only a provisional delimitation for the purpose of confirming Israel’s withdrawal under Resolution 425, without prejudice to the final determination of the boundary between Lebanon and Syria, but both Israel and Lebanon had said that they would respect this line.147 The Security Council repeatedly called for respect for the Blue Line.148 The Secretary-General reported that there were recurring violations of the Blue Line by Hezbollah and by Israel.149 These continued until a more serious conflict broke out in 2006.150 And there are still problems in 2017.

The Cold War conflicts demonstrated irreconcilable divisions among states on the question as to who could invite foreign military intervention, but they also show an impressive uniformity among states as to the prohibition of intervention to support armed opposition groups. States did not claim the legal right forcibly to overthrow a government; when they did aid the opposition they challenged the legitimacy of the government. The end of the Cold War did not bring an end to foreign intervention in civil wars, but it made it easier for the UN to play a much greater role in this area. The Security Council may now find it easier to pronounce on who is the government, partly because the UN may play a role in monitoring or supervising the conduct of elections as part of post-conflict peace-building. In recent years when the Security Council has imposed an arms embargo on a state after the outbreak of civil war it has sometimes subsequently made an express exception for the supply of arms to the government it regards as legitimate and also to states assisting that government.151

Thus the UN has often taken a clear view on the identification of the government and the right of states to support that government in a civil war. This practice indicates that it is not possible to assert that only a democratic government or only an effective government can invite military help.152 Thus in Mali, a transitional government came to power following a coup, and included some of the coup leaders; it was accepted by the Security Council although its origins were not democratic and it did not control the north of Mali.153 There was no (p. 105) challenge to the government’s right to invite help from France against Al Qaida terrorists (AQIM) in the north of its territory, and the Security Council welcomed ‘the swift action by the French forces at the request of the transitional authorities of Mali, to stop the offensive of terrorist, extremist and armed groups towards the south of Mali’ in Resolution 2100 (2013). Again, in Somalia the UN helped to create the Transitional Federal Government (TFG), and supported it in 2004–12, even though it had not been democratically elected, and was unable to assert its authority over the whole territory against the Union of Islamic Courts and later AlShabaab (joined to Al Qaida from 2012).154 When the TFG invited Kenyan troops to intervene against AlShabaab in 2011, the legality of this intervention was not challenged in the Security Council or elsewhere.155

In Libya the NATO-led military intervention authorized by the Security Council in 2011 led to the overthrow of the Gaddafi government.156 But there was no-one to fill the gap.157 Chaos ensued in the absence of a central government with a national army that could assert control over the territory. Competing militias fought for control of territory, airports, and oil resources, and the violence escalated to civil war in 2014. A Government of National Accord (GNA) was set up under the 2015 Libyan Political Agreement among some of the competing groups. It was at first based in Tunisia, and when it moved to Libya it did not exercise effective control over the whole territory and was challenged by a competing government and militias. Nevertheless the UN Security Council in Resolution 2259 (2015) (passed unanimously) expressly said that it was the ‘sole legitimate government’, and called on member states to respond urgently to its requests for assistance. In particular it urged member states to actively support the GNA in defeating ISIS; it called on them ‘to cease support to and official contact with parallel institutions that claim to be the legitimate authority’. In 2016 the AU, League of Arab States, and EU all recognized the GNA as the ‘sole legitimate government of Libya’, and stressed that the GNA was the sole legitimate recipient of international security assistance.158

(p. 106) However, the political divisions of the Cold War have resurfaced in recent years, and were manifest in the different approaches to the question who can invite military assistance in conflicts in Ukraine and Yemen. Russia denied using force to annex Crimea in 2014, but nevertheless suggested possible legal justifications for intervention in Ukraine.159 One of these was that there had been an anti-constitutional coup and the exiled President Yanukovych had invited its armed forces to act.160 Russia said that the democratically elected President had fled from the capital of Ukraine after violent protests stirred up by Western states, unhappy that he had abandoned his earlier pursuit of closer links with the EU. It could act on his invitation to protect the Russian population of Crimea against the threat allegedly posed by the new government. Similarly, Saudi Arabia’s justification for its military campaign in Yemen was that it had been invited in by elected President Hadi after he had fled from the capital to Saudi Arabia, and that it could assist him against the Houthi rebels. At an abstract level the two situations seem identical, but states generally rejected the legality of the Russian intervention in Crimea while accepting that of the Saudi operation in Yemen. Yanukovych’s invitation was dismissed as a pretext for the annexation of Crimea. In the Security Council, the UK said that there could be no invitation by a ‘former leader who abandoned his office, his capital and his country’.161 The UN General Assembly adopted Resolution 68/262 (2014) by 100–11–58; this called upon states to refrain from actions aimed at the disruption of the national unity and territorial integrity of Ukraine, including any attempts to modify Ukraine’s border through the threat or use of force.

In contrast the UN Security Council gave its express support to the Hadi government in Yemen, even though President Hadi had fled and resigned from his position.162 It repeatedly called for an end to attacks on the government; it also called on all states to refrain from military interference.163 When it met three weeks after the GCC began Operation Decisive Storm against the Houthi rebels, the Security Council did not make any criticism of the intervention. In Resolution 2216 (2015) passed by 14–0–1 (Russia) it once again called on the Houthis to end their use of violence. It also took note of President Hadi’s request for support, (p. 107) including military intervention, from the GCC. Only Iran contested the legality of the operation.164 In contrast, the UN Secretary-General recalled the Security Council’s earlier statement that states should not undermine sovereignty, independence, and territorial integrity, and should refrain from external intervention.165 The Security Council has not changed its position since then, despite public concern about the conduct of the military campaign and its impact on the population.166

Perhaps the most dramatic illustration of the principle that a government may invite outside assistance is that of Syria. It is this conflict that has stirred up commentators unhappy with the idea that a repressive regime may invite outside help (in this case from Russia and Iran) to keep itself in power; they have invoked internal self-determination and democracy in aid of their claims that there are limits on the right of a government to seek military assistance.167 But it is not only Russia and Iran that are allied to repressive regimes in the region, and the USA and the UK are reluctant to put forward any general claim that there is no legal right to support repressive or undemocratic regimes for fear that their own allies would be overthrown. The USA, Turkey, Saudi Arabia, and the other Gulf states have challenged the legitimacy of the Assad government and have intervened on the side of armed opposition groups since early in the conflict. But they have not denied that the Assad government has a legal right to invite outside assistance; they have made political and moral arguments against the legitimacy of the Assad government, as well as criticizing its military operations for violations of international humanitarian law. It is clear that they accept that Russia and Iran have a legal right to help Syria, to send troops and aircraft and to join in the military operations.168 This was powerfully illustrated by a leaked recording of the then US Secretary of State, John Kerry in 2016. He said that the USA had no legal grounds to attack Assad: ‘We don’t have a basis, our lawyers tell us, unless we have a UN Security Council resolution, which the Russians can veto and the Chinese, or unless we are under attack from the folks there, or unless we are invited in. Russia is invited in by the legitimate regime—well it’s illegitimate in my mind—but by the regime.’169 Thus, the US administration stuck to the traditional distinction between assistance to the government, even a repressive government, (lawful) and that to armed opposition forces (unlawful).

(p. 108) Forcible Intervention to Assist the Opposition

It is apparent from all the above practice that states will seek to invoke an invitation by a government to justify their invasion where this is even remotely plausible. They do not generally claim a legal right to use force to help the opposition forcibly to overthrow the government (with the possible exception of national liberation movements seeking decolonization), as the ICJ made clear in the Nicaragua case. Some writers have doubted the legal force of the prohibition of intervention to assist the opposition against the government because practice during the Cold War showed such extensive intervention to help oppositions.170 But they acknowledge that in fact those states helping the opposition have generally done so without use of their own troops; nor have they openly assisted opposition forces to operate from their territory.

The open use of a state’s own troops against a foreign government involved in civil conflict was rare. Covert action was much more common even in cases where the intervening state challenged the legitimacy of the government of the state involved in civil war. The USA, although it gave support to opposition groups in Angola, Cambodia, and Afghanistan, did not openly go beyond this to direct forcible intervention. Any direct use of force was generally, as in the Nicaragua case, carried out covertly through the Central Intelligence Agency (CIA). The supply of arms or training to opposition forces was generally covert and thus did not involve a need for legal justification. But it was in the massive financial support for opposition groups in Angola, Cambodia, Afghanistan, and Nicaragua under President Reagan that the USA seemed to come close to blatant disregard, if not rejection, of the legal principle of non-intervention. The President’s development of the ‘Reagan doctrine’ for the containment of the spread of socialism, with its rhetoric of the duty to help ‘freedom fighters’ against socialist governments, seemed to indicate that the USA was applying a new doctrine of national liberation; it was apparently adopting the doctrine developed by former colonies and socialist states during decolonization, the doctrine that it was legal for national liberation movements to use force in self-determination, to justify intervention in civil wars.171 But the Reagan doctrine was, like the Brezhnev doctrine, not put (p. 109) forward as a legal justification of the use of force; the right to use force was still based on self-defence.172 The aid was ostensibly limited to financial assistance, sometimes portrayed as ‘non-lethal’ or ‘humanitarian’ aid.173 In all these cases the USA challenged the legitimacy of the government it was attempting to subvert. Even in the middle of the Reagan era, however, the USA was not willing to try to justify its support for the contras in Nicaragua as based on the right to support oppositions forcibly to overthrow the government. In the Nicaragua case, as was discussed above, the USA did not rely on a legal right to intervene in support of ‘freedom fighters’, but rather on collective self-defence; this was clearly regarded as important by the Court.

After the terrorist attacks of 9/11 the international consensus on the prohibition on forcible intervention to overthrow a government apparently came under pressure from the actions and the rhetoric of the USA with regard to the regime change in Afghanistan and in Iraq in 2003. The USA nevertheless continued to accuse other states—in particular, Syria and Iran—of unlawful intervention against the new governments of Afghanistan and Iraq.174 When it began Operation Enduring Freedom in Afghanistan, the USA claimed to be acting in self-defence, but it subsequently went on overthrow the Taliban regime and install a new government. There were no real objections by other states with regard to the overthrow of the Taliban—the regime had been isolated in the international community, it had not been recognized by the UN as the legitimate government of Afghanistan and had been subjected to sanctions by the UN—but this question of regime change proved much more problematic with regard to Iraq.

Very soon after 9/11 the USA said that it wanted regime change in Iraq.175 Following President Bush’s identification of Iraq as part of the Axis of Evil in the 2002 State of the Union Address, the administration began to implement the 1998 Iraq Liberation Act signed into law by President Clinton at a time of political (p. 110) weakness, but never implemented by him. This provides that ‘It should be the policy of the United States to support efforts to remove the regime headed by Saddam Hussein from power in Iraq and to promote the emergence of a democratic government to replace that regime.’ Those states opposed to the use of force against Iraq, such as France, Russia, and China, all accused the USA of using force without legal justification in order to secure an illegal regime change.176 In contrast, the UK’s legal position was that it would welcome a regime change in Iraq if that was a consequence of its actions, but that this would not be the aim of any use of force. Whereas the US policy was regime change, it was not that of the UK; the UK’s purpose was disarmament.177 The Attorney-General in his advice on the legality of the war in Iraq expressly ruled out forcible regime change as the basis for the use of force; he said, ‘regime change cannot be the objective of military action’.178

However, the Nicaragua case suggests that in international law what is decisive is not the intent of the intervening state, whether proclaimed or otherwise. The test as to whether an act of intervention is unlawful is an objective one. In response to Nicaragua’s claim that it was the aim of the USA to overthrow the government the Court held that it did not consider it necessary to seek to establish whether the intention of the USA to secure a change of governmental policies in Nicaragua went so far as to be equated with an endeavour to overthrow the Nicaraguan government. The Court held that in international law, if one state, with a view to the coercion of another state, supports and assists armed bands in that state whose purpose is to overthrow the government of that state, that amounts to an intervention by the one state in the internal affairs of the other, whether or not the political objective of the state giving such support and assistance is equally far-reaching. It did not therefore examine the intentions of the United States in this context.179 The Court confirmed this approach in Armed Activities in the Territory of the Congo (DRC v Uganda).180

There have been no subsequent claims by states that they have a legal right to provide military assistance to armed opposition forces, although the behaviour of some states is obviously not consistent with the prohibition in Nicaragua. There have been many reaffirmations of the illegality of forcible intervention to secure regime change. Just as the Security Council with regard to the conflict in the DRC drew a distinction between outside forces invited by the government and those of Uganda and Rwanda, so with regard to other conflicts (p. 111) the Security Council has taken the same approach. When civil war broke out in Congo (Brazzaville) in 1997, Angola intervened and sent troops to support the opposition forces, which then secured victory. The Security Council, in a Presidential Statement, condemned outside intervention; it expressed concern about the grave situation and called for an end to hostilities. It condemned all external interference, including the intervention of foreign forces, in violation of the Charter of the UN and called for the immediate withdrawal of all foreign forces.181

The traditional position was again adopted with regard to intervention in the conflict in Sierra Leone. A civil war started in 1991 when opposition forces of the Revolutionary United Front (RUF) tried to overthrow the government. The RUF refused to accept the settlement ending the conflict and did not participate in the 1996 elections. It seized power in a military coup in 1997, but the UN refused to accept the overthrow of the democratically elected government under President Kabbah and this government was restored in 1998. The RUF continued their armed struggle. There were accusations that President Charles Taylor of Liberia was intervening to assist them to overthrow the government of Sierra Leone.182 Armed elements and criminal gangs operated across the borders; massive refugee flows aggravated the situation; the states in the region made accusations and counter-accusations of unlawful intervention.183 The Security Council called on all states in the region to take action to prevent armed groups from using their territory to prepare and commit attacks on neighbouring countries, but it singled out Liberia for express condemnation and sanctions. In Resolution 1343 (2001) it demanded that the government of Liberia immediately cease its support for the RUF in Sierra Leone and for other armed rebel groups in the region; called on it to expel RUF members from Liberia and to prohibit all RUF activities on its territory; and to cease all financial and military support to the RUF, including all transfers of arms and all military training. It imposed measures under Article 41 on Liberia and individual members of its government.184 Later it called on Liberian forces to refrain from unlawful incursions into Sierra Leone, and expressly determined that the active support by the government of Liberia to armed rebel groups in the region, including to rebels in Côte d’Ivoire and former (p. 112) RUF combatants who continued to destabilize the region, constituted a threat to international peace and security in the region.185

Another example is that of Somalia. When Eritrea was accused of intervention in Somalia on the side of armed groups which aimed to destabilize the region, the Security Council imposed sanctions on it in Resolution 1907 (2009), passed by 13–1 (Libya) –1 (China).186 This resolution demanded that Eritrea cease all efforts to destabilize or overthrow, directly or indirectly, the TFG. It called on all member states, ‘in particular Eritrea’, to cease arming, training, and equipping armed groups, including AlShabaab. After the Somalia/Eritrea Monitoring Group found that Eritrea had continued to provide support to armed opposition groups, including AlShabaab,187 the Security Council in Resolution 2023 (2011) condemned the violations by Eritrea of Resolution 1907. But later the Monitoring Group reported that it had found no evidence that Eritrea was supporting AlShabaab, though it did continue to support other armed groups. Some states called for a re-examination of the sanctions.188

The Non-Aligned Movement consistently proclaims the illegality of intervention to secure regime change,189 and in 2016 Russia and China issued a Joint Declaration on the Promotion of International Law. In this they fully supported the principle of non-intervention, and condemned as a violation of this principle any interference by states in the internal affairs of other states with the aim of forging change of legitimate governments.190 This may well seem hypocritical on the part of Russia in the light of its intervention in support of Russian separatists in eastern Ukraine since 2014. Following Russia’s annexation of Crimea, pro-Russian groups in eastern Ukraine also made claims to autonomy or independence against the government. A violent struggle ensued, and the government used heavy weapons and aircraft against the separatists. It denounced the opposing forces as terrorists.191 The conflict continued and intensified at the start of 2017 (p. 113) despite the 2015 Minsk ceasefire agreement.192 Almost 10,000 people have been killed and more than 1.7 million displaced.193 But Russia does not assert a legal right of intervention in support of an armed opposition, though it does maintain that the events in Ukraine had been provoked by ‘an externally supported coup d’etat’.194 In reply to the many accusations by Ukraine and by Western states, and despite the plausible newspaper reports of the presence of Russian troops in Ukraine, Russia maintained that any Russian troops are volunteers, veterans, or troops on holiday in Ukraine.195 The USA and UK also accuse Russia of equipping, arming, and training the separatists in violation of international law and the UN Charter.196


There is a striking similarity between Russia’s assistance to the armed opposition in Ukraine and that of the USA, the UK, Saudi Arabia, Qatar, Jordan, and Turkey to the armed opposition in Syria. But it is legally significant that in both conflicts those intervening on the side of the armed opposition did not assert a legal right to do so. In Syria, the popular uprising against the Assad government that began in 2011 turned into a prolonged sectarian conflict fuelled by foreign involvement, leaving over 250,000 dead, 5 million refugees, and 6.5 million internally displaced out of a total population of 22 million.197 Sunni states, including Saudi Arabia, Qatar, Jordan, and Turkey, assisted diverse armed opposition groups, as did the USA and the UK. The opposition included not only the Free Syrian Army (FSA), initially supported by the USA as the armed wing of the legitimate opposition, but also terrorist groups such as ISIS and the AlNusra Front (affiliated to Al Qaida ).198 These and other Islamist groups—despite the divisions between them—became militarily predominant among the opposition forces and succeeded in taking control of large areas of territory, not only in Syria but also in Iraq.199 Russia, Shiite Iran, and Hezbollah provided aid and intervened directly in support of the Assad government.200 Russia went on to take (p. 114) a more direct role in September 2015, when it began to supply fighter aircraft, helicopters, and tanks to the government and itself to carry out air strikes on opposition forces in response to their growing military gains.201

Intervention in Syria took different forms: first, certain states supplied arms, equipment, finance, and training (all classified as intervention in the Nicaragua case) to help opposing forces to overthrow the Assad government.202 Syria repeatedly accused them of unlawful intervention.203 Those states supporting the armed opposition did not attempt to provide a legal justification for their actions. The USA and UK at first gave what they claimed was ‘non-lethal’ aid as if that label made it lawful.204 Such aid did not initially include the supply of arms, but it did include night-vision goggles, protective gear, armoured vehicles, and communications equipment (all of which could be of direct use in conflict) as well as direct financial aid. But, as we have seen, the prohibition on intervention in the Nicaragua case is a wide one, and covers this type of assistance. The USA tried to challenged the narrative that in Syria it was on the same side as the terrorist groups it was fighting in Iraq by attempting to identify a moderate opposition and to assist this opposition to establish control over military forces. But the USA and UK faced the problem that the Free Syrian Army and its successors worked with Islamist groups, including the AlNusra Front and ISIS.205

This was of concern to Austria when the UK and France successfully secured the lifting of the EU arms embargo imposed in May 2011 on all groups in Syria, in order to allow the arming of the opposition.206 Austria had strongly opposed this move. It said that the Syrian National Coalition did not have full authority and control over all armed opposition groups, and cooperated with groups which included various extremist and terrorist fighters. The supply of arms to opposition groups would be a breach of the customary principle of non-intervention and the principle of non-use of force under Article 2(4). Austria cited the Nicaragua case and the Armed Activities case as support for its position. The supply of arms would (p. 115) also amount to a violation of Security Council Resolutions 1373 (2001) and 1624 (2005) establishing an arms embargo against individuals and entities associated with Al Qaida, in that weapons sent to the Free Syrian Army could end up in the hands of terrorist groups.207 That is, the prohibition of forcible intervention set out in the UN Charter Article 2(4) and the Declaration on Friendly Relations have been further developed in Security Council Resolutions passed after 9/11 imposing obligations to act against terrorists.208

There were also many consistent newspaper reports of covert aid by the USA, the UK, and France; they paid the salaries of opposition armed forces, provided intelligence, equipment, and training.209 The US President signed ‘secret covert action findings’ authorizing the CIA to provide arms to the rebels.210 Saudi Arabia and Qatar also provided very significant covert aid; they allowed the provision of arms and financial aid from 2012, with a significant increase in 2015.211 They did not openly claim a right to supply arms to opposition groups, and did not offer a legal justification. They have supported a range of different armed groups, including Islamist groups associated with the AlNusra Front.212 But just because aid to armed opposition forces is covert this does not mean that it does not have to be (p. 116) justified as a matter of international law. Syria repeatedly protested about Saudi Arabia’s support for terrorist groups.213

Turkey also played a major role in the conflict in Syria, but its interests did not completely coincide with those of the US-led coalition. Not only was Turkey hostile to Assad, who had in the past supported the terrorist PKK group of Turkish Kurds, it was also concerned about the threat it perceived from the Syrian Kurds in the YPG, one of the most successful opposition groups in fighting ISIS. Turkey allowed the Free Syrian Army to operate from its territory, and enabled the supply of arms and military equipment, with assistance of the CIA. It also allowed the infiltration of Islamist supporters across its border into Syria.214 It could be accused not only of active support to armed opposition groups, but also of violation of the duty of vigilance: of ‘acquiescing in organized activities in its territory directed towards the commission of terrorist acts, acts of internal strife’, as declared unlawful by the ICJ in the Armed Activities case.215 Syria sent hundreds of letters to the Security Council protesting about Turkey’s intervention, but Turkey offered no legal justification for its support for armed opposition forces.216

The next stage of intervention began after the international outcry about the 2013 chemical weapons attack, widely attributed to Assad government forces. The USA and the UK decided not to intervene directly against the Assad government to prevent future use of chemical weapons, but instead pursued a diplomatic agreement following a Russian initiative. The Assad government agreed to surrender its chemical weapons in the deal brokered by Russia and the USA in 2013.217 The USA continued to supply non-lethal aid, and also decided to supply arms to the forces of the Syrian Official Coalition, recognized by it as the legitimate government.218 It began to shift its public focus away from possible direct military action against the Assad government to the dangers posed by ISIS in Syria and Iraq and also to states outside the region.219 In 2014 the Security Council for the first time strongly condemned increased terrorist acts by organizations and individuals associated with Al Qaida, its affiliates, and other terrorist (p. 117) groups. It called on both the Syrian authorities and opposition groups to commit to combating those groups.220 It later went further: it identified the threat from ISIS, and decided that states should prevent the direct or indirect supply to ISIS from their territories or by their nationals of arms and related material.221 The US Congress now officially authorized train and equip programmes to help to establish a ‘moderate opposition’ against ISIS in September 2014, but these efforts were less than successful.222 Accordingly in October 2015 the USA shifted its approach to that of supplying existing groups, and in particular the Syrian Kurdish force, the YPG, which had had considerable success in its conflict with ISIS. The YPG formed part of the ‘Syrian Democratic Forces’ set up in October 2015.223 Clearly, assistance in the creation of such opposition forces and the provision of arms and other support to them in taking territory from ISIS could also pose a threat to the Assad government.224

Even more controversially, the USA and other states began direct military action in Syria on the legal basis of collective self-defence of Iraq and also, in some cases, of individual self-defence against attacks by ISIS: in August 2014 the USA began to carry out air strikes against ISIS and the AlNusra Front in Syria. This operation later became Operation Inherent Resolve and was joined by many more states, including Australia, Canada, France, Belgium, Denmark, and the Netherlands.225 The air strikes (and covert actions by special forces on the ground) were carried out without the consent of the Syrian government. Syria protested that ‘if any State invokes the excuse of counter-terrorism to be present in Syrian territory without the consent of the Syrian government … its actions shall be considered a violation of Syrian sovereignty. Combating terrorism in Syria requires close cooperation and coordination with the Syrian government.’226 In 2017 the USA (p. 118) under President Trump increased the number of air strikes against ISIS and Al Qaida , and also increased the number of US marines on the ground in Syria.227 It carried out a series of direct attacks on Syrian territory. In April 2017 it carried out a cruise missile attack on Syrian government targets in response to their alleged use of chemical weapons.228 Then, in May 2017, it attacked pro-Assad Iranian militias in southern Syria, apparently in defence of US special forces present on Syrian territory without the consent of the government. Those forces were on Syrian territory to assist anti-Assad rebels against ISIS, and apparently also to help them to keep control of the territory that they had recovered from ISIS.229 In June 2017 the USA escalated further and attacked a Syrian fighter jet that it accused of showing ‘hostile intent’ to coalition forces training and advising the anti-Assad rebels it supported.230 This was the first time that the USA had shot down a Syrian warplane during the conflict. Russia condemned the action as a ‘flagrant violation of international law’.231


Since the end of the Cold War (just as they did during the Cold War) states have continued to claim a legal right to maintain governments in power. In recent practice it seems that intervention to help a government against ‘terrorists’ is politically less controversial than intervention by superpowers to prop up friendly governments during the Cold War, and than neo-colonial intervention in former colonies to protect the interests of the colonial power. But intervention against terrorists is clearly just as open to abuse, and it is not possible to make the case that this is the only type of lawful intervention on the side of the government during a civil war.

In contrast, states do not claim a legal right to use force to secure regime change. Thus Russia denies intervention in Crimea and eastern Ukraine, even though its denials are not plausible. In Syria, as in the Nicaragua case, the USA does not rely on a right to intervene to overthrow a government; it invokes a controversially (p. 119) wide doctrine of self-defence to justify its military operations on Syrian territory without the consent of the government. The US Secretary of State has acknowledged that there is no legal right of forcible intervention on the side of the opposition. Nevertheless the USA has supplied ‘non-lethal’ aid and covert aid to armed opposition groups fighting to overthrow President Assad. The US military campaign since August 2014 has included (accidental) strikes against Syrian army forces232 and (deliberate) strikes on pro-Assad militias, as well as military support for ‘moderate’ armed opposition groups against ISIS. It is difficult to maintain the position that the USA is not in fact intervening in the conflict in Syria. Although the USA had justified its use of force in Syria on the basis that it was collective self-defence of Iraq and individual self-defence of the USA against ISIS and other terrorists, its support to armed opposition forces has prolonged the conflict and prevented Assad from achieving victory. The US Department of Defense asserted that the sole focus of its direct military operations in 2017 was on ISIS,233 but its actions brought the danger not only of clashes with Russia, as they pursue their competing agendas in Syria after the defeat of ISIS, but also of direct conflict with the Assad government.

The record of forcible regime change in the twenty-first century is not encouraging. The consequences have been felt not only in the states where a government has been overthrown, but also in the wider region. It is clear from the experience of Afghanistan, Iraq, and Libya that outside intervention on the side of armed opposition forces—even those depicted at the time as more moderate, or pro-democratic—leading to the military removal of a repressive regime may not produce a better outcome. Calls for regime change are destabilizing in that they may encourage both opposition forces and government authorities to prolong the armed conflict, leading to more deaths, displacement, and destruction of the infrastructure. There is a danger that any new government will lack legitimacy if it uses outside military assistance to seize power and if it continues to rely on outside troops for the maintenance of order and the provision of security. There are clear policy arguments underlying the strict prohibition on intervention against a government,234 and states like Brazil, India, and South Africa continue to express their strong support for the prohibition.235


1  See Chapter 6.

2  Human Security Report 2005, War and Peace in the 21st Century (2005) at 22–3. In 2016 the Deputy Secretary-General reported that the number of civil wars has tripled in the past ten years, UN Press Release GA/11781, 10 May 2016.

3  Arab League Pact Article 8 (70 UNTS 237); OAS Charter Article 15 (119 UNTS 48); OAU Charter (479 UNTS 70) Article 3; AU Constitutive Act Article 4(g) (2158 UNTS I 37733).

4  ICJ Reports (1986) 14 at para 191; ICJ Reports (2005) 168 at para 162.

5  ICJ Reports (1986) 14.

6  See Chapter 4.

7  Nicaragua case, para 184.

8  Nicaragua case, para 191.

9  Ibid, para 202.

10  Ibid, para 205.

11  Ibid, paras 206–9. The ICJ deliberately left on one side the question of the use of force by national liberation movements. Judge Schwebel, in his Dissenting Opinion, paras 179–80, was critical of this insofar as it indicated an exception to the principle of non-intervention.

12  Nicaragua case, para 246.

13  Ibid, para 228.

14  Ibid, para 241.

15  ICJ Reports (2005) 168, noted by Gathii, 101 AJIL (2007) 142.

16  For an account of events in the DRC, see 1998 UNYB 82, 1999 UNYB 81, 2000 UNYB 119, 2001 UNYB 116, 2002 UNYB 102, 2003 UNYB 113, 2004 UNYB 119. See also Okowa, ‘Congo’s war’, 77 BYIL (2006) 203.

17  On 23 June 1999 the DRC brought three cases before the ICJ against Burundi, Uganda, and Rwanda for acts of armed aggression in August 1998. It subsequently withdrew the cases against Rwanda and Burundi, but the case against Uganda continued and was decided in 2005.

18  They were apparently motivated in part by hostility to ex-President Mobutu; he had for many years supported União Nacional para a Independência Total de Angola (UNITA) opposition forces which had operated against their governments.

19  As a reflection of their involvement six states signed the Lusaka Ceasefire Agreement for the DRC on 15 July 1999: 1999 UNYB 87; Keesing’s (1999) 43051.

20  See 308 below.

21  1999 UNYB 81, 2000 UNYB 119-4, 2001 UNYB 116-36.

22  See, for example, UN docs S/2002/1202, S/2002/1187; 1999 UNYB 84, 2000 UNYB 122, 2001 UNYB 122.

23  2001 UNYB 140-5. Uganda, Rwanda, and Burundi objected to the April 2001 report, and the initial accusations against Burundi were dropped. The Expert Panel issued additional reports on the self-financing nature of the conflict and the continuing illegal exploitation of the DRC’s natural resources by state and non-state actors (UN docs S/2001/1072, S/2002/1146). Rwanda rejected the accusations that it was involved in the DRC for purely economic reasons; it maintained that it was concerned to prevent Rwandan opposition forces crossing into its territory; Uganda also said that the Final Report of the Panel ignored the fact that its forces were in the DRC for genuine security reasons; Zimbabwe and Angola drew a distinction between their position and that of the uninvited forces, UN docs S/PV 4642 (2002) at 2, 11, 15; S/PV4642 Res 1 at 18.

24  2000 UNYB 126, 129.

25  SC Res 1332 (2000), 1341 (2001), 1355 (2002).

26  SC Res 1417 (2002), paras 10, 12.

27  SC Res 1355 (2001), para 10.

28  Keesing’s (2001) 43932.

29  2003 UNYB 129; Keesing’s (2003) 45331; UN Press Release SG/SM/8785, 18 July 2003.

30  46 ILM (2007) 173; Report of the Secretary-General, UN doc S/2007/156, at para 21; UN doc S/PV 5603 (2006).

31  It also claimed that its troops were in the DRC with the consent of the government for part of the time, ICJ Reports (2005) 168, paras 92–105. The Court rejected this claim: see Christakis and Bannelier, ‘Volenti non fit injuria’, 50 AFDI (2004) 102.

32  ICJ Reports (2005) 168, para 41.

33  Ibid, para 162.

34  For further discussion of the Court’s treatment of self-defence in this case, see 174 below.

35  ICJ Reports (2005) 168, paras 148–65.

36  Ibid, para 165.

37  Ibid, paras 276–305.

38  Ibid, paras 297–9.

39  Ibid, paras 300–1.

40  Ibid, paras 302–3. The Court divided its consideration of Uganda’s first Counterclaim into three periods as suggested by the DRC.

41  Judges Tomka, Kooijmans, and Kateka argued that it was for the DRC to show that it had fulfilled its duty of vigilance and that in the absence of such evidence it was guilty of tolerating the activities of the rebels. Some commentators have made far-reaching claims about the consequences of a breach of the duty of vigilance in the context of the Syrian conflict, but these claims go far beyond the actual decision in the case. See Chapter 5.

42  See Nolte, Eingrefen auf Einladung (1999); Corten, ‘La rébellion et le droit international’, 374 Hague Recueil des Cours (2014) 53; Lieblich, International Law and Civil Wars (2013); Shattock, The legal limits of intervention by invitation of governments in civil wars (PhD, University of Cambridge, 2018).

43  ‘UK Materials on International Law’, 57 BYIL (1986) 614.

44  This relatively narrow conception of a civil war requires that the opposing forces control territory; this mirrors the provision in the laws of armed conflict set out in the 1977 Additional Protocol II to the 1949 Geneva Conventions Relating to the Protection of Victims of Non-International Armed Conflicts. Article 1 sets the threshold for the existence of a non-international armed conflict and the application of the Protocol at a high level, requiring that dissident armed forces or other organized armed groups exercise such control over part of its territory as to enable them to carry out sustained and concerted military operations and to implement this Protocol. The Protocol does not apply to internal disturbances and tensions such as riots, isolated and sporadic acts of violence, and other acts of a similar nature. This threshold is higher than that set in Common Article 3 of the 1949 Geneva Conventions. Article 1(4) of Additional Protocol I provided that conflicts involving national liberation movements should be categorized as international. See Fleck (ed), The Handbook of Humanitarian Law in Armed Conflicts (3rd edn 2013), Chapter 2.

45  See Wright, ‘Legal Aspects of the Viet-Nam Situation’, 60 AJIL (1966) 750; Falk (ed), The Vietnam War and International Law, 4 vols (1968, 1969, 1972, 1978).

46  1965 UNYB 185. The UN Secretary-General said: The escalation of the conflict in Viet-Nam was perhaps the most important of developments on the international scene which had repercussion on the UN. Paradoxically the problem was one in regard to which the Organization had not been able to take any constructive action, as was to some extent understandable since the settlement reached at Geneva in 1954 prescribed no role for the UN. Moreover, neither North Viet-Nam nor South Viet-Nam was a Member of the UN and parties directly interested in the conflict had openly voiced the view that the UN as such had no place in the search for a solution to the problem. This, of course, could not in itself prevent the UN from discussing the problem, but it did militate against the Organization being able to play a constructive role at the present stage.

47  See Gray, ‘Bosnia and Herzegovina: Civil War or Inter-State Conflict?’, 67 BYIL (1996) 155.

48  See, for example, Tadic Jurisdiction, 35 ILM (1996) 132; Tadic Judgment, 36 ILM (1997) 908; Tadic Appeal, 38 ILM (1999) 1518; Celebici, 38 ILM (1999) 57; Rajic, 91 AJIL (1997) 523.

49  See Brownlie, International Law and the Use of Force by States (1963), 327; Corten, The Law against War (2010), 288, 290; Corten, ‘La rébellion et le droit international’, 374 RCDI (2014) 53; Fox ‘Intervention by Invitation’ in Weller (ed), Oxford Handbook on the Use of Force in International Law (2015), 816.

50  See 233 below.

51  UN docs S/2013/17, S/2013/189, para 4. See also, Bannelier and Christakis, ‘Under the Security Council’s watchful eyes’, 26 Leiden JIL (2013) 855. On Operation Serval see <www.sdefnse.gouv.fr/operations/mali/dossier>. It terminated in July 2014 and was replaced by the larger regional force, Operation Barkhane, in partnership with Mauritania, Mali, Niger, Burkina Faso, and Chad.

52  ISIS (also known as ISIL) grew out of Al Qaida in Iraq (AQI) which had emerged after the 2003 US-led military operation against Saddam Hussein. AQI changed its name to ISIS in 2013, and declared a caliphate under the name of Islamic State in 2014. Al Qaida disowned ISIS in Feb 2014. On the rise of ISIS, see Report of the Secretary-General, UN doc S/2016/92.

53  Chulov, ‘Iran sends troops into Iraq to aid fight against ISIS militants’, The Guardian, 14 June 2014; Keesing’s (2014) 53441, 53768.

54  Iraq’s request, UN doc S/2014/691; US response, UN doc S/2014/695; UK response, UN doc S/2014/851. The USA not only carried out air strikes, it also sent in an increasing number of ground troops as ‘trainers’ of the Iraqi armed forces. In 2016–17 it increased the number of ‘advisers’ to assist the operations against ISIS. The UK has also provided nearly 1,000 ‘trainers’ on the ground.

55  Summary of the UK government legal position on military action in Iraq against ISIL, <www.gov.uk/government/publications/military-action-in-iraq-against-isil-government-legal-position>, 22 Sept 2014.

56  See account in 109 AJIL (2015) 199. See Bannelier-Christakis, ‘Military interventions against ISIL in Iraq, Syria and Libya’, 29 Leiden JIL (2016) 743.

57  On targeted killing, see 233 below.

58  For an account of the tactical shift in Somalia, see 110 AJIL (2016) 587; Roggio, ‘US military to actively target Shabaab in Somalia’, <www.longwarjournal.org/archives/2017/03/us-military-to-actively-target-shabaab-in-somalia.php>. On Yemen, see ‘US military hits AQAP with more than 20 airstrikes’, www.longwarjournal.org/archives/2017/04/us-military-hits-aqap-with-more-than-20-airstrikes.php>.

59  UN doc S/PV 4688 (2003).

60  See, for example, UN docs S/2012/131, S/2015/276, S/2015/873. Syria has repeatedly challenged the term ‘non-state armed opposition groups’ used in the Secretary-General’s Reports to the Security Council under SC Res 2139 (2014). See, for example, UN doc S/2017/339.

61  In 2015 Syria confirmed that it had invited Russia to cooperate in countering terrorism, UN docs S/2015/789, S/2015/792. Iran admitted that its troops were in Syria in May 2013, Keesing’s (2013) 52762. On Hezbollah’s assistance to the government, see Keesing’s (2013) 52577, 52699.

62  Its first resolutions to do so were SC Res 2139 (2014), SC Res 2170 (2014).

63  UN docs S/2013/492, S/2013/101.

64  See 113 below. The disagreements as to which groups were terrorists is also significant with regard to the implementation of ceasefire agreements in Syria; these allowed continued military action against terrorists. SC Res 2336 (2016) welcomed the efforts by Russia and Turkey to end violence in Syria after they brokered a ceasefire in December 2016. See Reports of the Secretary-General UN docs S/2017/339, S/2017/445, S/2017/541 for an account of the continued fighting.

65  See Sec-Gen Reports, UN docs S/2013/516, S/2015/624, S/2016/627, S/2016/1011.

66  SC Res 2214 (2015), 2259 (2015).

67  US Africa Command Press Release, 3 Aug 2016. The USA, the UK, and France have also sent in special forces on the ground. See Bannelier-Christakis, note 56 above, for discussion of earlier interventions in Libya by Egypt, the United Arab Emirates (UAE), and the USA. In contrast to the US reliance on consent by the GNA, France and Egypt did not seek an invitation to justify their attacks on terrorist groups in Libya: on France, see 110 AJIL (2016) 809; on Egypt see UN doc S/2015/120; Al Jazeera1, ‘Egypt launches strikes in Libya after Minya attack’, May 2017, <http://www.aljazeera.com/news/2017/05/egypt-launches-strikes-libya-minya-attack-170526200625281.html>.

68  UN doc S/PV 7927 (2017).

69  President Obama claimed that the military action in Libya was covered by the Authorization for Use of Military Force (AUMF) passed by Congress after 9/11 to authorize force against Al Qaida and associated groups. See 207 below.

70  See discussion by Bannelier and Christakis, note 56 above; Corten, The Law against War (2010) at 288; Lieblich, note 42 above at 155.

71  The impact of such facilities was indicated by the General Assembly in, for example, Resolution 51/427 (1996) on Bases and Installations on Non-Self Governing Territories, passed by 109-47-5. This expressed the strong conviction that military bases and installations in the territories could constitute an obstacle to the exercise by the people of those territories of their right to self-determination.

72  Moisi, ‘Intervention in French Foreign Policy’, in Bull (ed), Intervention in World Politics (1984), 67.

73  See 351 below (Côte d’Ivoire), 380 (Mali), 346 (CAR).

74  Alam, ‘Indian intervention in Sri Lanka and International Law’, 38 Neth ILR (1991) 346.

75  Keesing’s (1987) 35315.

76  26 ILM (1987) 1175.

77  India UN doc S/19354, Sri Lanka UN doc S/19355.

78  Keesing’s (2000) 43352, 43454, 43616, 43699, 43789, 43940.

79  Keesing’s (2001) 44339, (2002) 44606, 44609, 44931, (2003) 45234, (2005) 46938.

80  This was welcomed in SC Res 2307 (2016).

81  The Definition of Aggression Article 3(e) provides: ‘The use of armed forces of one state which are within the territory of another state with the agreement of the receiving state, in contravention of the conditions provided for in the agreement or any extension of their presence in such territory beyond the termination of the agreement.’ The delay by Russia in withdrawing their forces from the Baltic states (1994 UNYB 58, 576); by the UK in leaving Egypt (1947 UNYB 356); and by France in leaving Tunisia (1961 UNYB 101) were all the subject of complaint on this basis. Also the DRC claimed that Uganda’s continued use of force on its territory after its consent to the presence of the Ugandan forces had ended constituted aggression. The ICJ avoided any specific finding of aggression, but it did hold that Uganda was guilty of a violation of Article 2(4): ICJ Reports (2005) 168 at paras 42–54, 92–105, 110–11, and 165.

82  For a fuller account, see 3rd edn of this book at 85.

83  The UN Secretary-General expressed concern at the entry of the GCC troops, UN Press Release SG/SM/13445, 14 Feb 2011. See Corten, ‘La rébellion et le droit international’, 374 RCDI (2014) 53 at 161.

84  UN doc S/2011/253. The GCC accused Iran of interference, UN doc S/2011/253.

85  1956 UNYB 67. The only states defending the USSR were from the socialist bloc.

86  1968 UNYB 298.

87  UN doc S/PV2932 (1990).

88  For a fuller discussion of this practice, see the 3rd edn of this book, at 88. See Chapter 4 on the use for force in protection of nationals abroad without the consent of the territorial state.

89  1964 UNYB 95; see Virally, ‘Les Nations Unies et L’Affaire du Congo’, 1960 AFDI 557; Abi-Saab, The United Nations Operation in the Congo 1960–1964 (1978).

90  2000 UNYB 195; UN doc S/PV 4139 (2000); Statement by the Secretary of State for Defence in the House of Commons, 15 May 2000. See Chapters 6 and 8 on peacekeeping in Sierra Leone.

92  Keesing’s (2000) 43552, (2001) 44330, 2000 UNYB 195, 207. The UK forces remained until July 2002 (Keesing’s (2002) 44888); they returned briefly in February 2003 because of concern about possible destabilization as a result of the conflict in Liberia (Keesing’s (2003) 45231; UN doc S/PV 4577 (2002).

93  1965 UNYB 140; Meeker, ‘The Dominican Situation in the Perspective of International Law’, 53 Department of State Bulletin (1965) 60.

94  The GA condemned the intervention in GA Res 38/7 (1983) (108-9-27). The condemnation by the Security Council was vetoed by the USA: 1983 UNYB 211. See Gilmore, The Grenada Intervention (1984).

95  1989 UNYB 172.

96  Keesing’s (1989) 37113; D’Amato, ‘The Invasion of Panama was a Lawful Response to Tyranny’, 84 AJIL (1990) 516; Henkin, ‘The Invasion of Panama under International Law: A Gross Violation’, 29 Col J Trans L (1991) 293.

97  On the regional peacekeeping justification also used in the Dominican Republic and Grenada, see Chapter 8.

98  Both these episodes show the absence of a clear line between helping a government to deal with outside subversion and collective self-defence; it was not always obvious which argument the government was relying on. But the distinction does not affect the right to send troops into the state to help the government; it only affects the scope of the right to use force. See Chapter 4 on collective self-defence.

99  UN doc S/PV1441(1968), para 133; 1968 UNYB 299.

100  On the relationship between the Brezhnev doctrine and earlier US justification for its intervention in the Dominican Republic, see Franck and Weisband, Word Politics (1972).

101  1968 UNYB 299.

102  Keesing’s (1991) 38687.

103  Keesing’s (1989) 36982; see Gray, ‘Self-Determination and the Break-Up of the Soviet Union’, 12 European YIL (1992) 465.

104  1980 UNYB 296 at 298, 299.

105  GA Res 35/37 (1980) (111-22-12), 1980 UNYB 296, 308.

106  Keesing’s (1991) 38437; (1992) 38725.

107  For a discussion of the Cyprus intervention and the interpretation of the Treaty of Guarantee, see Ronzitti, Rescuing Nationals Abroad (1985) at 117–34; Necatigil, The Cyprus Question and the Turkish Position in International Law (1989); 1974 UNYB 256.

108  SC Res 351, 353, 355, 356, 358, 359, 360, 361 (1974), etc.

109  This was the position of Angola, Namibia, and Zimbabwe as regards their intervention to assist the government of the DRC against Rwanda and Uganda: see 176 below.

110  Keesing’s (1980) 30261.

111  Keesing’s (1987) 35110.

112  Keesing’s (1991) 38564, (1992) 38755.

113  Keesing’s (1981) 30687, 31165.

114  The United Nations Blue Book Series, Vol V, The United Nations and Mozambique 1992–1995 (1995), 11.

115  1957 UNYB 57; 1958 UNYB 36, 41: 1960 UNYB 194; 1961 UNYB 149; Weisburd, Use of Force (1997) 184, 187.

116  For a general account of the conflict in Chad, see Weisburd, Use of Force (1997), 188; Alibert, ‘L’affaire du Tchad’, 90 RGDIP (1986) 368.

117  1981 UNYB 222.

118  For a fuller discussion, see third edn of this book at 107.

119  For an account of events, see Ruys and Ferro, ‘Weathering the storm’, 65 ICLQ (2016) 61.

120  First as President of North Yemen from 1978 and then, after the unification of North and South Yemen in 1990, as President of the whole of Yemen.

121  UN doc S/2015/217.

122  See Ruys and Ferro, note 119 above.

123  UN docs S/PV 7411 (2015), S/PV 7426 (2015), S/2015/266.

124  UN doc S/2015/279; ‘Yemen crisis: Kerry warns Iran over Houthi rebel support’, <http://www.bbc.co.uk/news/world-middle-east-32229316>. For Iran’s reply, see UN docs S/2015/207, S/2015/249, S/2015/335.

125  UN docs S/2016/73, S/2017/81.

126  UN doc S/2015/263.

127  Ibid, para 54; UN doc S/2017/81, para 55.

128  See Roth, Governmental Illegitimacy in International Law (1998).

129  Doswald Beck, ‘The Legal Validity of Military Intervention by Invitation of the Government’, 56 BYIL (1985), 189; Mullerson, ‘Intervention by invitation’ in Damrosch and Scheffer (eds), Law and Force in the New International Order (1991), 13; Nolte, Eingreifen auf Einladung (1999).

130  For an account of Syria’s presence in Lebanon, see Report of the Secretary-General, UN doc S/2004/777.

131  An indication of this special relationship was that there were no diplomatic relations between the two states; they did not maintain embassies on each other’s territory. The Security Council later called for the establishment of normal diplomatic relations in Resolutions 1680 (2006).

132  For an account of the conflict in Lebanon, see Weisburd, Use of Force (1997), 155.

133  Bregman and El-Tahri, The Fifty Years War (1998), 157–60.

134  Keesing’s (1976) 27765; Report of the Secretary-General, UN doc S/2004/777 at para 4, 13.

135  1978 UNYB 371.

136  1982 UNYB 428.

137  1984 UNYB 285.

138  1984 UNYB 285; UN doc S/PV 2556 (1984), UN doc S/17694 (1985).

139  UN doc S/PV 2640 (1986). In 1991 Lebanon and Syria concluded two treaties. The first in May was on coordination and cooperation; Lebanon would not allow forces hostile to Syria to operate from its territory and joint councils would coordinate policy. The second agreement in September was a mutual defence treaty. These agreements formally recognized the special position of Syria (1991 Annual Register 215).

140  UN doc S/PV 5028 (2004).

141  UN doc S/PV 5122 (2005).

142  The UN SC established an International Commission of Inquiry into the assassination by Resolution 1595 (2005). In SC Res 1757 (2005) the SC provided for the establishment of an international tribunal to try those found responsible for any terrorist crime.

143  UN doc S/PV 5172 (2005).

144  SC Res 1614 (2005), SC Res 1655 (2006), SC Res 1680 (2006).

145  Report of the Secretary-General UN doc S/2004/777 at paras 18–21.

146  Report of the Secretary-General UN doc S/2000/460. Both Syria and Lebanon said that they regarded the territory as part of Lebanon.

147  Report of the Secretary-General UN docs S/2000/460, S/2000/564, S/PV 4146 (2000), S/PV 4160 (2000).

148  S/PRST/2000/21, 18 June 2000; SC Res 1583 (2005), 1614 (2005).

149  Secretary-General’s Reports UN docs S/2004/777, S/2005/272, S/2005/673, S/2006/248, S/2006/832; UN docs S/PV 5241 (2005); S/PV 5175(2005); S/PV 5352 (2006).

150  See 213 below.

151  See 276 below.

152  De Wet, ‘The modern practice of intervention by invitation in Africa’, 26 EJIL (2015) 979; Roth, ‘Secessions, coups and the international rule of law’, 11 Melbourne JIL (2010) 393; Corten, note 42 above; LeMon, ‘Unilateral intervention by invitation in civil wars’, 35 NYUJILP (2003) 741.

153  See Report of the Secretary-General, UN doc S/2013/189, UKMIL in 84 BYIL (2013) 801. See Bannelier and Christakis, note 51 above.

154  For a more detailed account of the background, see Chapter 6.

155  See Kenya’s letter to the UNSC, UN doc S/2011/646. On Kenya’s possible additional justification of self-defence against AlShabaab in response to a series of kidnappings in Kenya, see also Chapter 5. The Monitoring Group on Somalia and Eritrea reported that ‘the principal impediments to security and stabilization in southern Somalia are the TFG leadership’s lack of vision or cohesion, its endemic corruption and its failure to advance the political process’, UN doc S/2011/433.

156  See Chapter 7.

157  For criticism of the failure to plan for the aftermath of the military operation, see UK Foreign Affairs Committee, Third Report of Session 2016–17, Libya: Examination of intervention and collapse, HC 119, 14 Sept 2016. This failure is all the more disappointing in the light of past experience in Afghanistan and Iraq where the overthrow of the Taliban and Saddam Hussein governments had led to prolonged insecurity.

158  SC Res 2238 (2015); Joint Communique on Libya, Brussels, 22 Sept 2016, Unique ID:160922_11, EU External Action Service.

159  UN docs S/PV 7124, 7125 (2014); Bilkova, ‘The use of force by Russia in Crimea’, 75 ZaöRV (2015) 27.

160  UN doc S/PV 7125. Russia also said that it had been invited into Crimea by the Prime Minister. However, commentators generally agree that only the highest state authority may invite outside intervention. See, for example, Nolte, ‘Intervention by Invitation’, Max Planck Encyclopaedia on Public International Law; Corten, ‘The Russian intervention in the Ukrainian crisis’, 2 Journal on the Use of Force and International Law (2015) 17; Simma et al. (eds), The Charter of the UN: A Commentary (3rd edn 2012), 214.

161  UN doc S/PV 7125; the USA and France also accused Russia of violating Ukraine’s sovereignty.

162  Ruys and Ferro, note 119 above.

163  SC Res 2051 (2012), SC Res 2140 (2014), SC Res 2201 (2015).

164  UN doc S/2015/263.

165  UN Press Release SG/SM/16621, 26 March 2015.

166  UN doc S/PV 7871 (2017).

168  Syria’s invitation, UN doc S/2015/789; Russia’s response, UN doc S/2015/792.

169  For the audio recording, <www.nytimes.com/interactive/2016/09/30/world/middleeast/john-kerry-syria-audio.html>. For the text of the relevant passage, see Yuhas, ‘Kerry audio leak’, The Guardian, <www.theguardian.com/us-news/2016/oct/01/syria-strikes-audio-john-kerry-russia-warns-us>, 1 Oct 2016.

170  Lowe, ‘The Principle of Non-intervention: Use of Force’, in Lowe and Warbrick (eds), The United Nations and the Principles of International Law (1994), 66; Weisburd, Use of Force (1997), 1–27. See contra, Mullerson, ‘Sources of International Law: New Tendencies in Soviet Thinking’, 83 AJIL (1989) 494.

171  Reisman, ‘Old Wine in New Bottles: The Reagan and Brezhnev Doctrines in Contemporary International Law and Practice’, 13 Yale JIL (1988) 171; Reisman, ‘The Resistance in Afghanistan is Engaged in a War of National Liberation’, 81 AJIL (1987), 906 and (1988), 82. Reisman seems to go further than the US government in his argument. Vertzberger, Risk Taking and Decisionmaking; Foreign Military Intervention Decisions (1998), demonstrates that despite the belligerent rhetoric President Reagan’s administration in fact took a cautious attitude to intervention.

172  Kirkpatrick and Gerson, ‘The Reagan Doctrine, Human Rights and International Law’, in Henkin (ed), Right v Might (1991), 19. D’Amato also was insistent that the doctrine did not involve the forcible overthrow of the government: ‘The Secret War in Central America and the Future of World Order’, 80 AJIL (1986) 43 at 111.

173  Keesing’s (1986) 34426; (1987) 35121, 35174; (1988) 35896. This pretence seems to have come near to being abandoned in 1987 with reports of the direct supply of Stinger missiles to the opposition forces in Angola and Afghanistan: Keesing’s (1987) 34864; (1988) 35786. Some of these weapons ended up in the hands of the Iranian opposition and of Qatar: Keesing’s (1998) 36220, 36313.

174  For accusations against Syria, see, for example, Keesing’s (2005) 46651,46714; for accusations against Iran, see, for example, Keesing’s (2005) 46905, (2007) 47679, 47780, 47867, (2007) 47679, 47722, 47780, 48063, 48102. Some of these accusations expressly allege government responsibility for intervention; others are more general claims that there is intervention by Syrian or Iranian groups or from the territory of Syria and Iran.

175  Foreign Affairs Committee Seventh Report of Session 2001–02, Foreign Policy Aspects of the War Against Terrorism, HC 384, para 204; Second Report of Session 2002–03, HC 196, para 111. See Reisman, ‘Why regime change is (almost always) a bad idea’, 98 AJIL (2004) 516.

176  UN docs S/PV 4726 and 4726 Res 1 (2003).

177  UKMIL, 73 BYIL (2002) 877 at 16/43.

178  AG’s Advice on the Iraq War, 54 ICLQ (2005) 767 at para 36.

179  Case concerning Military and Paramilitary Activities in and against Nicaragua, ICJ Reports (1986) 14 at para 241.

180  ICJ Reports (2005) 168 at para 163.

181  S/PRST/1997/47; 1997 UNYB 112.

182  In 2003 Charles Taylor was indicted for war crimes and crimes against humanity for his part in the conflict in Sierra Leone; he is facing trial before the Special Court for Sierra Leone. On UN and regional peacekeeping in Sierra Leone, see Chapters 6 and 8.

183  Guinea accused Liberia and Burkina Faso of support for armed opposition to its government; Liberia accused Guinea and Cote d’Ivoire (2000 UNYB 180, 182; 2001 UNYB 180, 2002 UNYB 186–7; Reports of the Secretary-General UN docs S/2003/466, S/2002/494; UN doc S/PV 4405 (2001); Keesing’s (2000) 43737, 43781, (2001) 43933, 43985, 44041, 44141, (2002) 44605).

184  See Secretary-General’s Reports on Liberia’s compliance with these demands: UN doc S/2002/494; 2001 UNYB 184, 186; 2002 UNYB 168.

185  SC Res 1408, 1436 (2002) para 13; SC Res 1478 (2003).

186  UN docs S/2008/769, S/2009/388.

187  UN doc S/2011/433. The Group did, however, note that Eritrea’s support for such groups could only be understood in the context of its unresolved border dispute with Ethiopia. The SC had not taken any action on Ethiopia’s continued occupation of Eritrean territory. See 157 below.

188  See, for example, UN docs S/2014/727, S/2015/801, S/PV 7626 (2016) Russia, Senegal, China, and Venezuela; S/PV 7925 (2017).

189  Most recently, in the declaration issued at the 17th summit (2016), <www.8.irna/en/News/82235410/> when they reaffirmed their commitment to non-intervention, and rejected the illegal policy of regime change aimed at overthrowing constitutional governments. See also UN doc S/2014/573.

190  <www.rusemb.org.uk/fnapr/5645>. Though note the flexibility offered by the use of the word ‘legitimate’. See also Foreign Policy Concept of the Russian Federation (approved by President Putin on 30 Nov 2016), Document 2232-01-12-2016.

191  For example, UN doc S/PV 7154 (2014); Application of the International Convention for the Suppression of the Financing of Terrorism and of the International Convention on the Elimination of All Forms of Racial Discrimination, (Provisional Measures) Ukraine v Russia, ICJ Reports 2017, paras 2, 25.

192  The SC supported the Minsk Agreement in SC Res 2202 (2015).

193  UN doc S/PV 7876 (2017).

194  UN doc S/PV 7683 (2016).

195  For example, the accusations by Ukraine, the USA, and the UK in UN doc S/PV 7154 (2014); UK in UKMIL 85 BYIL (2014) 365–6, 617–18. Russia’s position is that the pro-Russian forces in Ukraine are not its agents and do not carry out operations under its effective control, and that therefore they do not meet the Nicaragua threshold for attribution of a violation of the prohibition of the use of force.

196  UN doc S/PV 7576 (2015), S/PV 7683 (2016),

197  According to the United Nations High Commissioner for Refugees (UNHCR).

198  It changed its name in 2016 and announced that it had split from Al Qaida , but this was rejected by the USA and Russia.

199  Keesing’s (2013) 53094, (2014) 53147, 53208, 53716, 53767.

200  Keesing’s (2012) 52408, 52243; (2013) 52762, 52816. Hezbollah was designated as a terrorist organization by the GCC and the Arab League in 2016 (though this was not supported by Iraq and Lebanon), as it had been earlier by the USA, and by the EU as regards its military wing, ‘Arab League brands Hezbollah a terrorist organization’, <www.bbc.co.uk/news/world-middleeast-35789303>.

201  UN docs S/2015/789, S/2015/792; Keesing’s (2015) 54284.

202  Keesing’s (2012) 51070, 51015. For early Syrian protest at outside intervention, see UN doc S/2011/353. See also Ruys, ‘Of arms, funding and non-lethal assistance’, 13 Chinese JIL (2014) 13; Gray, ‘The Limits of Force’, 376 Hague Recueil des Cours (2014) 101.

203  See, for example, UN docs S/2011/353, S/2015/388, S/2016/703.

204  Keesing’s (2013) 52520, 52634, 52762. See, for example, UK Foreign Secretary William Hague, Oral Statement to Parliament, UK response to developments in Syria, 12 Sept 2013 <www.gov.uk/government/speeches/uk-response-to-developments-in-syria-and-chemical-weapons.ar>; Statement on Syria, 13 Jan 2014, HoC Hansard Vol 573 col 583–4; UKMIL, 83 BYIL (2012) 343–5; 85 BYIL (2014) 621. The UK and other states also funded a massive public relations campaign by the ‘moderate opposition’.

205  Keesing’s (2013) 53044, (2014) 53716, 53767.

206  UKMIL, 84 BYIL (2013) 797; Keesing’s (2013) 52699.

207  As, for example, in Nov 2013, Statement on Syria, 13 Jan 2014, HoC Hansard Vol 573 col 583–4.

208  Syria also made this argument, as for example in UN doc S/2013/348.

209  Keesing’s (2013) 52577; Borger, ‘Britain may arm Syrian rebels to save lives if conflict intensifies, says Hague’, The Guardian, 4 March 2013; Borger and Hopkins, ‘West training Syrian rebels in Jordan in drive to counter Islamists’, The Guardian, 9 March 2013.

210  Hosenball, ‘Exclusive – Obama authorizes secret US support of Syrian rebels’, Reuters, 1 Aug 2012; Keesing’s Record of World Events (2013) 52762; deYoung and Gearan, ‘US citing use of chemical weapons by Syria, to provide direct military support to rebels’, The Washington Post, 13 June 2013; The Guardian, 24 July 2013; these authorizations were apparently for small arms only, and the USA was slow to actually deliver the weapons. See Londoño and Miller, ‘US weapons reaching Syrian rebels’, The Washington Post, 12 Sept 2013. In July 2017 it was reported that the CIA was to end its covert programme to arm anti-Assad rebels in Syria, Jaffe, and Entous, ‘Trump ends covert CIA program to arm anti-Assad rebels in Syria’, The Washington Post, 19 July 2017, <https://www.washingtonpost.com/world/national-security/trump-ends-covert-cia-program-to-arm-anti-assad-rebels-in-syria-a-move-sought-by-moscow/2017/07/19/b6821a62-6beb-11e7-96ab-5f38140b38cc_story.html?utm_term=.5f74d16776a9>.

211  Wezeman, ‘Arms Transfers to Syria’, SIPRI Yearbook (2013) 269; Keesing’s (2013) 52520, 52700, 52987, 53044; Khalif and Fielding Smith, ‘Qatar bankrolls Syrian revolt with cash and arms’, The Financial Times, 16 May 2013; Black, ‘Saudis to spend millions fighting two wars in Syria’, The Guardian, 8 Nov 2103; Black, ‘Syrian rebels should be sent heavy weapons’, The Guardian, 26 Jan 2013; Gardner ‘Gulf Arabs stepping up arms supplies to Syrian rebels’, BBC, 8 Oct 2015, <www.bbc.co.uk/news/world-middle-est-34479929>. On Jordan’s role, see Hubbard, ‘Warily, Jordan assists rebels in Syrian War’, New York Times, 10 April 2014, <www.nytimes.com/2014/04/11/world/middleeast/syria.html?ref=world&_r=1>.

212  See, for example, Keesing’s (2013) 52987, 53044. In 2017 Saudi Arabia accused Qatar of supporting terrorists and imposed an embargo on its territory: Wintour, ‘Gulf plunged into diplomatic crisis’, The Guardian, 6 June 2017, <https://www.theguardian.com/world/2017/jun/05/saudi-arabia-and-bahrain-break-diplomatic-ties-with-qatar-over-terrorism>.

213  See, for example, UN doc S/2013/151, S/2013/533, S/2013/625, S/2013/727, S/2013/766, S/2014/66, S/2016/703. For Saudi Arabia’s position, and Syria’s reply see UN docs S/2014/92, S/2014/209.

214  See Hosenball, ‘Exclusive – Obama authorizes secret US support of Syrian rebels’, Reuters, 1 Aug 2012; Chulov, ‘Saudis plan to fund rebel Syrian army’, The Guardian, 23 June 2012; Syrian accusations UN doc S/2013/98; Turkey’s reply UN doc S/2013/101; see also Syrian letters UN docs S/2013/137, S/2013/151.

215  ICJ Reports (2005) 168, paras 162, 300.

216  For example, UN docs S/2013/713, UN S/PV 7316 (2014) 33, S/2014/207, S/2014/223, S/2015/276, S/2016/703, A/68/882.

217  Keesing’s (2013) 52926; SC Res 2118 (2013).

218  ‘Current Developments’, 107 AJIL (2013) 654.

219  See the Sec-Gen’s reports on ISIL, UN docs S/2016/92, S/2016/501, S/2016/830, S/2017/97.

220  SC Res 2139 (2014), para 14.

221  SC Res 2161 (2014), SC Res 2170 (2014), SC Res 2199 (2015), paras 24–7.

222  US Congressional authorization of aid to Syrian opposition, HJ Res 124 Sec 149, 19 Sept 2014. This authorized the provision of training, equipment, and supplies to appropriately vetted element of the Syrian opposition to defend the Syrian people from attacks by ISIS and to secure territory controlled by the Syrian opposition. The aim was to train 5,000 troops to fight ISIS, but only four survived, ‘Syria crisis: only four or five US-trained Syrian rebels are still fighting’, BBC, 17 Sept 2015, <www.bbc.co.uk/news/world-middle-east-34278233>.

223  Keesing’s (2015) 54348, 54411. The US supply of arms to the YPG led to disagreement with Turkey which portrayed them as allies of the PKK, and which did not want to see a Kurdish enclave on the Syrian/Turkish border. Gordon and Schmitt, ‘Trump to arm Syrian Kurds, even as Turkey strongly objects’, The New York Times, 9 May 2017, <www.nytimes.com/2017/05/09/us/politicas/trump/kurds-syria-army.html>. Turkey had led FSA forces in Syria against the YPG in Operation Euphrates Shield from August 2016 to the end of March 2017, see 195 below. It subsequently continued its air strikes against the YPG in Syria in 2017, claiming self-defence as its justification, UN doc S/2017/350.

224  For continuing Syrian protests, see for example, UN docs S/2014/372, S/2017/183.

225  On the self-defence justification, see 237 below.

226  Syria also protested repeatedly at the targeting of its infrastructure by the coalition aircraft, as for example in UN docs S/2014/846, S/2015/719, S/2017/183. Henderson, ‘The use of force against Islamic State’, 1 Journal on the Use of Force (2014) 209.

227  AP, ‘US sends hundreds of marines to Syria to support fight against ISIS’, The Guardian, 9 Mar 2017 <www.theguardian.com/us-news/2017/mar/09/us-sends-hundreds-of-marines-to-syria-to-support-fight-against-isis>.

228  See 118 above.

229  ‘Syria war: US-led coalition strikes pro-Assad convoy’, BBC, 18 May 2017 <www.bbc.co.uk/news/world-middle-east-39969585>; ‘Syria and Russia condemn US-led attack on pro-Assad forces’, BBC, 19 May 2017 <www.bbc.co.uk/news/world-middle-east-39972271>.

230  <https://www.defense.gov/News/Article/Article/1220818/dod-official-sole-focus-in-iraq-syria-remains-on-isis/>. The USA also shot down Iranian drones over Syria: Wintour and Borger, ‘Russia threatens to target US warplanes’, The Guardian, 20 June 2017.

231  Filipov and Loveluck, ‘Russia threatens to treat US coalition aircraft as targets over Syria’, The Washington Post, 19 June 2017.

232  ‘Syria conflict: US air attack endangers truce’, BBC, 18 Sept 2016 <www.bbc.co.uk/news/world-middle-east-37400810>.

233  ‘Coalition Defends Partner Forces from Syrian Fighter Jet Attack’, Operation Inherent Resolve, CJTF-OIR, 19 June 2017. The statement said ‘The Coalition’s mission is to defeat ISIS in Iraq and Syria. The Coalition does not seek to fight Syrian regime, Russian or pro-regime forces partnered with them, but will not hesitate to defend Coalition of partner forces from any threat.’ <http://www.inherentresolve.mil/News/Article/1217917/coalition-defends-partner-forces-from-syrian-fighter-jet-attack/>.

234  See Gray, ‘Limits on Force’, note 202 above.

235  For example, UN docs S/PV 7527 (2015) at 48, 77, 80; S/PV 7621 (2016). Many other states continue to reaffirm the Charter principles of sovereign equality and non-intervention.