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International Law and the Use of Force, 4th Edition by Gray, Christine (15th February 2018)

1 Law and force

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, 2015. All Rights Reserved.date: 21 February 2020

Self-defence — Crimes against humanity — Genocide — War crimes — Armed conflict — UN Charter — International peace and security

(p. 1) Law and force

The world in 2018 seems a dangerous place, and the legal constraints on the use of force imposed by the UN Charter after the Second World War have come under great pressure. The number of conflicts within states has been increasing since 2010, and the number of people displaced by conflict has reached 65 million, the highest figure since the Second World War. Three conflict-torn states have produced half the world’s refugees: Afghanistan, Somalia, and Syria. Traditional large-scale inter-state conflicts remain uncommon, but militarily powerful states have turned to the use of military force to attain political ends in Georgia, Ukraine, Syria, Libya, Yemen, and elsewhere. New conflicts have broken out in recent years in South Sudan, the Central African Republic (CAR), and Mali.1 Many older conflicts are unresolved.2 The attempts by President Obama to disentangle the USA from the conflicts in Iraq and Afghanistan have failed. The risks of cyber-warfare are much discussed.

New threats to the peace in the Far East have arisen out of China’s assertive measures in support of its extravagant claims to almost the whole of the resource-rich (p. 2) and strategically vital South China Sea. There is a danger of conflict involving China, Vietnam, Indonesia, Malaysia, the Philippines, and Taiwan—states with competing territorial and maritime claims—and also the USA, Australia, and Japan. The East China Sea is another potential flashpoint between China and Japan. Tension has risen between India and China because of their border dispute in the Himalayas. There is danger also from North Korea’s defiance of the Security Council’s demands that it end its nuclear weapons testing and firing of long-range missiles, measures said by North Korea to be a defensive response to threats of pre-emptive military action by the USA. The deterioration of relations between Russia and the West is another factor contributing to the current precarious situation. It may not be appropriate to speak of the revival of the Cold War, but the renewed hostility between the USA and Russia has led NATO to re-focus on its original role of collective self-defence of the territories of its member states against a perceived threat from Russia. Just as it had during the Cold War, Russia relied on arguments used earlier by Western states in its attempt to justify its major military intervention in Georgia (2008) on the basis of a wide right of self-defence of nationals abroad.3 In contrast, Russia (implausibly) denied military intervention in Crimea and eastern Ukraine for a considerable period, while at the same time suggesting a series of possible justifications, including the protection of its nationals.4

The hopes of the Arab Spring (2011) have been shattered, and the repercussions of the conflicts in North Africa have been felt far beyond the region directly involved.5 The conflicts that broke out following attempts to overthrow repressive leaders in Libya, Syria, and Yemen have brought renewed attention to the principle of the prohibition of intervention to which states still pay lip-service. These conflicts have raised further legal questions, first: as to whether there can be a right of unilateral humanitarian intervention to protect citizens from their own governments, given the strong opposition of the vast majority of states to this doctrine. Second, as to the content of the more recent doctrine of Responsibility to Protect (R2P)—the responsibility of the ‘international community’ to protect a population from war crimes, genocide, and crimes against humanity by the government. Third, and most important, the conflict in Syria has brought renewed debate about scope of the right to self-defence in counter-terrorism operations.

In the early days of the Arab Spring, the uprising against the government of Colonel Gaddafi in Libya (2011) was supported by Western states with little (p. 3) planning for the outcome; they had all too clearly not learned the lessons of Iraq where the overthrow of Saddam Hussein in 2003 by a US-led coalition had led to prolonged instability and the rise of Al Qaida in Iraq. The Security Council authorized the use of force to protect civilians in Libya, and its Resolution 1973 (2011) was controversially interpreted by NATO as allowing it to provide direct military support for armed opposition forces, leading to the overthrow of Colonel Gaddafi. Some hailed this as a triumph for R2P, but the military operation confirmed the suspicion felt by many states towards a doctrine which they saw as a pretext for regime change by powerful states. The intervention was followed by the total breakdown of security in Libya. The flow of arms and fighters from Libya contributed to instability in the Lake Chad Basin states where Boko Haram has been active for many years; it also contributed to an uprising in the north of Mali involving not only separatist groups, but also AQIM, an affiliate of Al Qaida. AQIM continues to carry out attacks on government and UN forces in Mali; France has sent troops to assist the government of its former colony to recover control of its territory from the terrorists.

Next, the uprising against President Assad in Syria escalated to a sectarian conflict with outside intervention by regional rivals Saudi Arabia, Qatar, and Turkey, in support of diverse opposition groups, and Iran, in support of the government. The terrorist group ISIS flourished as the conflict continued, and its dramatic advances and seizure of territory in Iraq and Syria drew world attention in 2014.6 The USA’s direct military intervention in Syria against ISIS (without the consent of the Syrian government), and in support of the ‘moderate’ armed opposition, and that of Russia in support of the Assad government led some commentators to call for a reappraisal of the law on intervention. In 2017 President Trump has taken direct military action in Syria against the Assad government, in response to the use of chemical weapons by government forces, and to protect opposition forces supported by the USA from attack by pro-Assad forces. Little by way of legal justification of these actions was put forward by the USA, and there is widespread concern that the USA under President Trump will not pay attention to legal constraints, that it will neglect diplomacy and peaceful settlement (especially in relation to Iran and North Korea), and that its actions will be unpredictable.

Finally, in Yemen (2012) President Saleh was ousted after nearly forty years in power following popular protests, but his successor was driven out of the country by opponents including Houthi rebels allegedly supported by Iran. Saudi (p. 4) Arabia (backed by the USA and the UK) led a massive military intervention at the request of the new President, in pursuit of its regional rivalry against Iran. This has led to a devastating conflict and a humanitarian crisis in one of the poorest countries in the world, though one of great strategic significance. The violent insecurity has enabled another affiliate of Al Qaida, AQAP, to increase its activity in Yemen.

The rise of ISIS in Iraq and Syria, and the attacks carried out by its adherents in the West (in Paris, Berlin, Brussels, London, and elsewhere), the continued activity by Al Qaida and its affiliates, including AlShabaab in Somalia, AQIM in Mali, and AQAP in Yemen, all show that the ‘global war on terror’ proclaimed by US President George W Bush after the 11 September 2001 attacks on the USA, and continued by President Obama as a war on ‘Al Qaida and its affiliates’, has not been won. Indeed, the experience of the last fifteen years indicates that it is unlikely ever to be won by military means. Terrorist groups in Asia, the Middle East, and Africa have proclaimed adherence to Al Qaida or to its offshoot, ISIS. In 2017 there has been significant progress towards the end of ISIS’ control of territory in Iraq and Syria, but there are still fundamental divisions in those states, and ISIS’ affiliated groups and individual supporters still pose a threat outside those states. The US programme of ‘targeted killings’ of suspected terrorists begun by President Bush after 9/11, and vastly increased by President Obama, is now being pursued and further expanded by President Trump in Afghanistan (where he used the ‘mother of all bombs’ against Al Qaida suspects), Pakistan, Somalia, and Yemen. The justification for these targeted killings remains a wide and controversial claim to self-defence.

It is clear that the ‘war on terror’ is not a technical legal term,7 and it is argued by many to be a misleading and unhelpful term. The question arises how far this language is simply a rhetorical device, designed by the USA to legitimate the weakening of constitutional protection of human rights, the increase in military spending, the expansion of bases round the world, the imposition of pressure on certain states, and the pursuit of US foreign policy actually driven by other considerations.8 There is a danger that the language of the ‘war on terror’ will (p. 5) not only glorify those more properly regarded as criminals, and exaggerate the threat that they pose, but that it will also distort our understanding of particular conflicts, just as during the Cold War the perception of many conflicts in ideological terms distorted their true nature and obstructed their effective solution. This danger is intensified when leaders speak of the ‘war on terror’ as one against a single enemy.9 Moreover, the Secretary-General has expressed concern that the war against terrorism will detract from other equally, if not more, pressing dangers—sometimes categorized as ‘soft threats’—such as threats of extreme poverty, unsafe drinking water, the disparity of income between and within society, the spread of infectious diseases, or climate change and environmental degradation.10

Nevertheless, the rhetoric of the ‘war on terror’ has some significance for the law on the use of force in that it has been used to justify a wide right of self-defence against non-state actors, and to threaten pre-emptive action to prevent certain states, accused of state sponsorship of terrorism, from developing nuclear weapons. There are significant differences between states, and between commentators, on these issues. In pursuit of those responsible for the terrorist attacks of 9/11, and on the basis of a right of self-defence against terrorist attacks, the USA initiated Operation Enduring Freedom in Afghanistan, an operation which continues today under a new name. But President Bush then widened the focus of the war against terrorism beyond Afghanistan. In his famous State of the Union Address of January 2002 he singled out the states of the ‘Axis of Evil’—Iran, Iraq, and North Korea—as posing a threat to the USA. He argued that there was a danger that such ‘rogue’ states would develop chemical, biological, and nuclear weapons of mass destruction (WMD) for use against US targets or for supply to terrorists hostile to the USA. In response to its perception of a fundamentally changed international situation, the USA put forward a new 2002 National Security Strategy, including the controversial doctrine of pre-emptive self-defence. This doctrine was not accepted by other states or in the various reports on the future of collective security produced by UN bodies after the 2003 Iraq conflict.11 The consensus was that no change in the UN Charter provisions on the use of force (p. 6) was necessary. The fundamental prohibition on the use of force in Article 2(4), the right of self-defence in Article 51, and Chapter VII on collective action were all adequate to meet the new threats.12

However, challenges to the Charter framework have continued and even intensified. President Obama may have chosen to abandon the language of pre-emptive self-defence, but in its place he developed a wide counter-terrorism doctrine that seemed identical in substance.13 A few other close allies have followed this approach. Many states joined the USA in its battle against ISIS in Iraq, and some also joined in the more controversial operations in Syria; they invoked collective self-defence of Iraq, and some (including France and the UK) have also claimed a wide right of individual self-defence against future terrorists attacks on their own territory. It is in this context of counter-terrorism, and following its policy on targeted killing, that the USA developed a radical new doctrine allowing self-defence, against ‘imminent attacks’ (very widely construed) by suspected terrorists in a state determined by the USA to be ‘unwilling or unable’ to take action against them in a way acceptable to the USA.14

Thus there is a renewed debate about international law on the use of force, its content, and effectiveness. It has been the object of challenge in the past, most recently in the context of the controversial 2003 military operation against Iraq. Some commentators used apocalyptic language and mourned the death of Article 2(4), the prohibition of the use of force in the UN Charter.15 In contrast others welcomed the end of the Charter system and of any international law constraint on the USA.16 Yet others argued that international law was evolving to meet new threats, and welcomed the changes they identified in the law on self-defence, intervention, and regime change.17 Some were content for the USA to claim special rights exercisable exclusively by it as the only remaining superpower.18 Now once again there is debate about the effectiveness and legality of the use of force.

(p. 7) It remains to be seen how far states are today deliberately posing a challenge to the whole UN system and to the existing international legal order, or whether they are operating within the system, even if manipulating the rules for their own ends. The apparently cynical manipulation of legal rules is nothing new, disingenuous rhetoric is certainly not unique to the international legal system. Thus, the question arises whether lip-service to international law on the use of force is meaningless or to be welcomed as indicating continued adherence to the Charter system? The approach to be taken by the Trump administration is not yet clear.

The UN Security Council has not been able to play an effective role in ending some of the conflicts mentioned above, in part because of the political differences among the five permanent members. But states have turned to the UN for legitimacy and support in the difficult task of the reconstruction of states, as in Afghanistan, Iraq, and Libya. There is a great demand for UN peacekeeping and post-conflict peacebuilding. In the twenty-first century the UN has played a major role in ending serious conflicts, especially in Africa where it has increasingly acted in cooperation with regional organizations. The prospects for peace in Sierra Leone, Liberia, and Côte d’Ivoire are encouraging, and the situation facing the hybrid UN/African Union (AU) force in Darfur is much improved. Two UN peacekeeping forces have been terminated in 2017 and one has been significantly reduced in size.19 Past problems have increased awareness of the need to prevent the resurgence of conflict after the conclusion of a peace agreement or political settlement, and after the withdrawal of UN peacekeeping forces. But there is also an increased determination not to maintain peacekeeping forces beyond their useful life, and to plan for a clear exit strategy for all operations.20

The major surge in peacekeeping in 2003 brought with it serious difficulties in securing troops and equipment, and also calls for increased cooperation with regional organizations and for a reappraisal of peacekeeping doctrine. The African host states of several UN operations are pressing for a more robust approach to peacekeeping; some of them challenge the traditional principles of peacekeeping—of impartiality, consent, and use of force only in self-defence. The UN operations in the Democratic Republic of Congo (DRC) and Mali brought controversial innovations. In the DRC the revolutionary Intervention (p. 8) Brigade created as part of the UN force was given the power to ‘neutralize armed bands’. This unusual new mandate provoked much controversy, even though it was said to be ‘on an exceptional basis and without creating a precedent’.21 In Mali the UN force had to operate in a lawless area under attack by terrorist groups. In response, the 2015 Report on Uniting Our Strengths maintained its support for the fundamental principles, at least in peacekeeping operations when there was some form of ceasefire or agreement before the UN force was deployed.22 The Report acknowledged that the principles might not be so suitable where peacekeeping operations are sent into ongoing armed conflicts, but it maintained the long-standing position that UN peacekeeping operations are not well suited to enforcement measures or to counter-terrorism operations. The UN has therefore increasingly turned to regional organizations, and especially to the African Union (AU) as first responders in ongoing armed conflicts where there is no peace to keep, as in Somalia, the CAR, and Mali. However, the previous debate as to whether the growing reliance on regional organizations should entail greater autonomy for them in decision-making on the use of force, and even a right to take enforcement action without Security Council authorization, has largely died down. The AU turns to the UN for authority to use force and for the logistical, financial, and other support necessary to carry them out.

Another area of debate with regard to peacekeeping is the use of force in protection of civilians during armed conflict or from non-state violence. Ever since the 1994 Rwandan genocide and the failure of the Security Council to authorize military action, there has been growing pressure on UN peacekeeping operations to protect civilians under threat of violence. Two missions in Africa were recently established with this as their express priority. The 2015 Report recommended that there should be an implied power for all peacekeeping operations to use force for this purpose, and that where operations are given an express mandate to protect civilians they should exercise this in a pro-active way. But even this task brings difficulties. It has become clear that such a mandate ought to be combined with the pursuit of a political solution. It is still under consideration how the protection of civilians is to be combined with other aspects of an operation’s mandate, especially if the mission has been given a robust mandate. The peacekeeping force in South Sudan (the UN’s newest member state), established after the end of a twenty-five year civil war between North and South Sudan, was assigned the protection of civilians as its priority, but it has faced serious difficulties in the implementation of this mandate because of the outbreak of violence between factions competing for power and resources.

(p. 9) This book will examine the use of force since the UN Charter; the focus will be on state and UN practice under the Charter.23 The aim is to identify the areas of agreement and disagreement, to examine through practice the application and development of the law in the light of the Charter framework, and to provide enough primary material to enable the reader to decide between the sometimes radically opposed interpretations of the same practice. The rest of this chapter has two main interrelated subjects: first, the problems with the identification of international law on the use of force in the light of the fundamental disagreements between states and between commentators, and second, the role of international law in this area and the complexities of any inquiry into its effectiveness.

Identification of the Law

The starting point for any examination of the law is the prohibition of the use of force in Article 2(4) of the UN Charter.24 Irrespective of whether the UN Charter is seen as a revolutionary departure from existing customary international law on the use of force or as a codification of rules that had already undergone a major shift in the twentieth century,25 the Charter system was a marked departure from that of the League of Nations and the language of Articles 2(4) and 5126 provides a new terminology and the first expression of the basic rules in their modern form. States may still occasionally use the rhetoric of ‘war’, in the language of the Covenant of the League of Nations, but the drafters of the UN Charter deliberately chose to use the wider term ‘use of force’ in the prohibition in Article 2(4).27 The rules of the Charter on the use of force are brief and cannot constitute a comprehensive code.28 The provisions in Articles 2(4) and 51 are very much a response (p. 10) to the Second World War and are accordingly directed to inter-state conflict.29 It is now a commonplace that such conflicts, or at any rate large scale inter-state conflicts, have proved to be the exception in the years since 1945; and that civil wars, with or without outside intervention, have outnumbered traditional inter-state wars.30 Cross-border terrorist attacks and limited inter-state fighting in border areas have been more common than all-out wars between states. The struggles of national liberation movements for independence during the decolonization process also did not fit easily into the framework of Articles 2(4) and 51. The evolution of rules to cover these conflicts is a complex process. Even in inter-state conflicts the apparently simple words of the Charter have given rise to fundamental differences between states.

The use of force is one of the most controversial areas of international law; even from the early days of the UN many disagreements between states (between developed and developing, between East and West) as to the law were apparent. The prohibition of the use of force led to fundamental divisions as to whether the ‘use of force’ included economic coercion, the scope of the right of self-defence, the right to use force to further self-determination, and to intervene in civil wars. These differences emerged in the context of the Cold War and the decolonization process. The end of the Cold War, the overwhelming military dominance of the USA as the one remaining superpower, and the virtual end of decolonization led to calls for a reappraisal of international law on the use of force by states and by UN forces. Subsequently, the proliferation of nuclear weapons and the emergence of terrorist groups such as Al Qaida and ISIS have raised further questions about the scope of the right to use force. How far should the Charter be interpreted to allow the use of force to respond to terrorist attacks, to restore or further democracy, to restore order in a state without an effective government, to further the right to self-determination outside the decolonization context and to prevent the proliferation of nuclear weapons? How far should the UN Security Council exercise centralized control over these and other uses of force?

How, if at all, can these controversies, old and new, as to the scope of the right to use force be resolved? A central question is whether it is possible to use state practice to arrive at an authoritative interpretation of the Charter or to supplement its brief provisions. Is it possible to find standards by which to assess the legality of states’ actions and which advisers can use to give guidance to states? Given that state practice may include the actual use of force, complicity in that use of force, the justification offered by states for it, the response of other states inside and outside the UN and other organizations, and their public positions in debates on general resolutions of the General Assembly on the use of force, as well (p. 11) as an extensive treaty practice including friendship treaties, non-aggression pacts, border treaties, mutual defence agreements, and regional arrangements, how are universal rules to be extracted? Questions also arise as to who speaks for a state: is it to be the US President or the US State Department Legal Adviser, the UK Prime Minister or the UK Attorney-General? Should the Charter be seen as open to dynamic and changing interpretation on the basis of subsequent state practice or should the prohibition of the use of force in Article 2(4) rather be seen as having a fixed meaning, established in 1945 on the basis of the meaning of the words at that date in the light of the preparatory works and the aims of the founders?31

In recent years there has been a renewed interest in the question of the appropriate methodology for the identification of the rules in this area of the law. Many writers pay little attention to the Charter framework: their focus is on recent practice, and often on the practice of a small group of states. They typically attach little weight to the reaction of other states, and implicitly equate silence with support.32 But few states are today willing to speak out individually against the USA’s use of force, apart from a small group of those consistently critical of it (including Russia, to a lesser extent China, Iran, Cuba, North Korea, Venezuela, and Nicaragua). Weaker states are more willing to reaffirm the need for strict adherence to the Charter and to the peaceful settlement of disputes in general statements issued through the Non-Aligned Movement (NAM). Thus in 2014 the NAM issued a final document setting out its adherence to the principle of non-intervention and rejecting ‘the illegal policies of regime change’. It asserts that Article 51 of the UN Charter is restrictive and should not be re-written or reinterpreted.33

Some argue that legal rules must be what they call ‘realistic’ in the sense that they do not constrain the use of force by powerful states against terrorists or to prevent proliferation of nuclear weapons.34 Such commentators may seek to rationalize the use of force by states; they offer a fuller justification than that actually given by the state using force and they attempt to reconcile the use of force with the (p. 12) UN Charter.35 The danger of this type of approach is that, at the worst, commentators may enable the use of force by states; at best, they may serve as apologists for states claiming a wide right to use force. Others take a stricter, positivist approach, explicitly based on the Charter provisions and on the practice of the full range of states.36 But even these writers do not necessarily come to agreement about the content of the law.37 They may disagree as to what counts as state practice, whether it includes statements as well as actions, whether it is possible to weigh statements, to distinguish between specific and abstract statements, and as to the significance of silence.

The International Court of Justice (ICJ) in the Nicaragua case apparently regarded the Charter provisions as dynamic rather than fixed, and thus as capable of reinterpretation over time through state practice. However, such interpretation could not go so far as to contradict the words of the Charter. The Court acknowledged that ‘The UN Charter … by no means covers the whole area of the regulation of the use of force in international relations’ and went on to explain that the Charter provisions on self-defence needed to be supplemented by the customary international law requirements of ‘necessity and proportionality’; it also examined customary international law on the meaning of ‘armed attack’ and the ‘use of force’.38 On the fundamental principles as to the use of force contained in Article 2(4) the parties agreed that the Charter provisions represented customary law, and even ius cogens, and the Court accepted this without going into the question of how far the meaning of Article 2(4) was fixed or how far it had evolved over time. However, it apparently accepted in theory the possibility of the development of new law on forcible intervention allowing a new exception to the prohibition of the use of force in Article 2(4). That is, it seems to have accepted the possibility of a dynamic interpretation of the customary law rules contained in Articles 51 and 2(4) based on the development of state practice.39

(p. 13) Almost from the time of the creation of the UN the states parties worked to elaborate on the provisions of the UN Charter on the use of force in General Assembly resolutions. Western states often evinced some unease about this process. During the Cold War the UK and the USA tended to argue that Article 2(4) should be treated as the last word, for fear that any modification would be to the advantage of the Soviet Union.40 But the Western states have come to accept the legal significance and customary international law status of certain of these resolutions. This process of elaboration on the UN Charter began with the 1949 Resolution on the Essentials of Peace. The ICJ in the Nicaragua case in 1986 singled out the 1974 Definition of Aggression41 and the 1970 Declaration on Friendly Relations42 to help it to identify customary international law on the non-use of force. These resolutions have since been supplemented by the 1987 Declaration on the Non-Use of Force.43 But even though these resolutions adopted unanimously or by consensus may be seen as authoritative interpretations of the UN Charter or as contributing to the formation of customary international law,44 they often left controversial issues unresolved.

Typically the price of consensus was ambiguity on the crucial issues that divide states. The drafting history of the resolutions reveals more about the views of states than the resolutions themselves.45 Thus the central question of the scope of the right of self-defence was not dealt with in the General Assembly resolutions. This issue divided states which took a wide view, such as the USA, Israel, the then apartheid-state, South Africa and, to a lesser extent, the UK and France, from the vast majority of other states. These states claimed a right to use force to protect nationals abroad, to take anticipatory self-defence, and to respond to terrorism as part of self-defence. The vast majority of states rejected such claims before the events of 9/11. But it seems that states preferred to avoid any substantive provision on this question of self-defence and this enabled them to maintain (p. 14) their opposing positions. During the debates on the 1987 Declaration on the Non-Use of Force only the USA and Australia spoke out expressly in favour of anticipatory self-defence; the other states were able to maintain their positions simply through the omission of any provision on self-defence apart from the general formula that ‘States have the inherent right of individual or collective self-defence if an armed attack occurs, as set forth in the Charter of the UN’.46

Also the General Assembly resolutions could not settle the controversies that divided developed and developing states as to the meaning of ‘force’, as to the right to use force in the furtherance of self-determination for colonial peoples or to recover territory illegally seized by another state. Nor did the resolutions resolve the dispute as to the legality of use of nuclear weapons. These differences manifested themselves during the debates on the Declaration on Friendly Relations from 1962; the same differences continued to divide states during the ten years’ drafting of the Declaration on the Non-Use of Force and the end product did not constitute any real advance on the Declaration on Friendly Relations.47

The vast mass of actual use of force reveals that states almost always agree on the content of the applicable law; it is on the application of the law to the particular facts or on the facts themselves that the states disagree. Of course it may be difficult to keep these three categories entirely separate, as is clear from the rather repetitive judgment of the ICJ in the Nicaragua case. The Court drew the distinction between the facts, the law, and the application of the law to the facts, but it found itself unable to maintain a strict distinction, especially between the last two categories.

It is clear that in the overwhelming majority of cases of inter-state use of force both states involved invoke self-defence against an armed attack by the other state. The only disagreement in the mass of cases of limited cross-frontier action is over the questions of fact whether there was a cross-border incursion or who began the conflict. This may occur in up to a hundred minor incidents a year. The UN may receive reports from both sides but is not often in a position to assign responsibility. Thus most state practice in inter-state conflicts, even if one of the parties is breaking the law, does not lead to any need to reappraise the content of the law. Similarly, in civil wars states seem from their practice to agree that forcible intervention to help the opposition overthrow the government is unlawful whereas assistance to a government may be legal. This is the position consistently expressed by states since the Second World War,48 and even in the Syrian conflict (p. 15) this apparently remains their position.49 The questions that divide the intervening states are questions of fact, and application of the law to those facts: who invited help; was there a genuine invitation; was it a civil war or mere internal unrest; was there already foreign intervention. State responses to forcible intervention show a lack of doubt about the law; they generally condemn if they think the intervening state was trying to interfere.

Until recently the mass of practice on minor episodes received relatively little academic examination. The focus of writers, especially American writers, was on US practice and, to a lesser extent, the practice of Israel; they were less concerned with the use of force in Africa and Asia or even with the use of force in the Soviet Union/Russia or involving China. There was also comparatively little discussion of the law on the use of force in continental European journals until 9/11 and Operation Iraqi Freedom; these journals also showed a rather more surprising concentration on US practice and relatively little discussion of the use of force by their own states or by their own former colonies. But all this has changed. Since the third edition of this book in 2008 there has been a massive increase in the amount written on the law on the use of force. There are new specialist journals, many new handbooks, about a hundred new monographs, and endless blogs. It is no longer true that the discussion of state practice is almost exclusively focused on that of the USA.

The past focus on US practice could in part to be explained by the fact that in general the USA often offered rather fuller articulations of its legal position than did other states using force. Also many of the episodes involving the USA were unlike the vast mass of state practice in that they did reflect differences between states as to the applicable law; the state using force took a controversial position as to the content of the law in order to justify its use of force. The protection of nationals, as in Iran, Grenada, and Panama, the extension of this doctrine of self-defence to cover actions in response to terrorism against Libya in 1986, against Iraq in reaction to the alleged assassination attempt on ex-President Bush in 1993, and against Afghanistan and Sudan in 1998 all produced clear divisions between states, apparent in the debates on these particular incidents and in general debates. In contrast, the USSR in attempted justification of its use of force generally put forward legal doctrines that were unexceptionable in themselves; it was their application that was controversial. The USSR claimed invitation by the government and collective self-defence to justify its intervention in Hungary, Czechoslovakia, and Afghanistan. In these episodes the disagreement was on the facts (had there been an invitation, who had given the invitation, was there outside intervention) rather than as to the law. Similarly, its successor, Russia, has (p. 16) relied on doctrines already espoused by western states to justify its use of force in Georgia and Ukraine.

More recently, the Syrian conflict has produced deep divisions between states as to the law on self-defence. The USA at the end of President Obama’s term of office published a controversial new legal framework on the use of force in counter-terrorism reflecting its practice in Syria and its targeted killing programme outside areas of active hostilities.

The natural focus of writers on controversial episodes where the law relied on by the states using force was not generally agreed, rather than on the mass of state practice where the law was not controversial, may have the side-effect of giving a misleading overall picture. The impression that emerges may be one of greater uncertainty than the total picture would justify, even after 9/11 and Operation Iraqi Freedom. How far does looking at the broader picture of all states’ uses of force produce a different view of the law from that produced on the basis of more limited practice? In any one year media reports give the largest list of conflicts; many of the minor episodes reported are never referred to the UN. Some conflicts may be referred to the UN in state communications but may not be officially debated, or may be debated only in secret; some conflicts may be debated but not lead to the adoption of a resolution or a statement; if a resolution is adopted, it may be legally indeterminate.

In early years it was more common for minor incidents to be referred to the UN and debated. Higgins wrote in 1963 that even minor episodes were the subject of condemnation by the Security Council; this is no longer the case.50 Should the episodes in which the UN has been involved be considered more important in the establishment or confirmation of legal rules? In practice it is not surprising that they tend to attract more academic discussion. But states have various motives for choosing to refer or not to refer matters to the UN and whether or not to seek a debate. In the early years the UN Yearbook specifically listed ‘Matters raised but which the Security Council did not consider’; these tended to be matters dealt with by the Organization of American States (OAS) and this heading was later temporarily dropped.51 The Secretary-General in his annual report has from time to time mentioned the failure of states to refer their conflicts to the UN; he has (p. 17) acknowledged that they may have had good reasons for this, but also has said that failure to turn to the UN may bring the organization into disrepute.52

The Security Council clearly has an important role, but there is controversy as to whether its findings are conclusive as to legality, illegality, and as to the content of the applicable norms.53 How far is the law developed by institutions? That is, do states acting collectively through the UN have a more important role than they do outside the UN in the interpretation and application of the UN Charter? Does the Security Council have the final say not only as to what is an act of aggression, threat to the peace, or breach of the peace under Chapter VII of the Charter, but also as to what is a threat or use of force under Article 2(4) or an armed attack and as to whether a state is acting in self-defence under Article 51? This question as to the scope of Security Council powers is important because the end of the Cold War has brought vastly increased activity by the Security Council. Whereas commentators used to discuss the problem of the inactivity of the Security Council, now they also concern themselves also with difficulties over the legitimacy of its actions.54

The debate as to whether judicial review of the Security Council’s resolutions on the use of force is possible and desirable has revived with the end of the Cold War; this issue whether it should be the ICJ rather than the Security Council that has the final word on the validity of determinations under Article 39 of the UN Charter and decisions on action under Chapter VII has come up before the ICJ in a few cases.55 To date, the ICJ has avoided a categorical answer to the sensitive question as to whether it may allow judicial review of Security Council decisions. Commentators are divided as to whether in principle judicial review should be available or whether it would be incompatible with the primary responsibility (p. 18) of the Security Council for the maintenance of international peace and security ‘in order to ensure prompt and effective action by the United Nations’ under Article 24 of the UN Charter.56 But the Court did make clear in its discussion of admissibility in the Nicaragua case that it does not regard itself as excluded from deciding on cases involving ongoing armed conflict including decisions as to collective self-defence. It asserted the right of the Court to resolve any legal questions, saying that the Security Council had only primary, not exclusive, authority under Article 24 of the UN Charter. Moreover, the Court had not in the past shied away from cases merely because they had political implications or involved serious elements of the use of force. The USA itself had brought cases involving armed attacks. ‘As to the inherent right of self-defence, the fact that it is referred to in the Charter as a “right” is indicative of a legal dimension; if in the present proceedings it becomes necessary for the Court to judge in this respect between the parties it cannot be debarred from doing so by the existence of a procedure for the States concerned to report to the Security Council in this connection.’57

Encouraged by this reasoning, several states have subsequently brought cases to the Court on this sensitive subject matter of the use of force. Cameroon brought a boundary case against Nigeria, in which it also made allegations that Nigeria had illegally undertaken cross-border incursions;58 Iran sued the USA in two cases arising out of US involvement in the 1980–8 Iran–Iraq conflict, first, the Oil Platforms case,59 and, second, a case arising out of the shooting down of the Iran Airbus by a US warship;60 Yugoslavia brought cases against ten NATO states for their bombing campaign over Kosovo;61 Pakistan sued India for shooting down a Pakistani aircraft over Pakistani air-space;62 the DRC sued Burundi, Uganda, and Rwanda for acts of armed aggression perpetrated in flagrant violation of the UN Charter; it claimed that the invasion by respondent state troops in an attempt to overthrow the government was a violation of the DRC’s sovereignty (p. 19) and territorial integrity.63 As it turned out, the Court has not given decisions on the merits in many of these cases and it avoided the question of the use of force in Cameroon v Nigeria.64 More recently it again avoided going into the question of the legality of the use of force in Certain Activities Carried out by Nicaragua in the Border Area65 and in Alleged Violations of Sovereign Rights and Maritime Spaces in the Caribbean Sea.66 However, it did go out of its way to discuss the law on self-defence at some length in the Oil Platforms case.67 And it gave an important judgment on the use of force, intervention, and self-defence in the Case concerning Armed Activities on the Territory of the Congo (DRC v Uganda).68 The Court has generally taken a restrictive approach to the legality of the use of force.69 It has also been cautious in that it has avoided controversial issues such as anticipatory self-defence, the use of force against non-state actors, and nuclear weapons.70

The question has also arisen of the role of the General Assembly and its relationship to the Security Council in the development and application of the law in this area.71 Chapter IV of the UN Charter gives some guidance on the role of the General Assembly and the division of functions between the two organs of the UN. Under Article 10 the General Assembly may make recommendations to member states or to the Security Council; Article 11(1) says that the General Assembly may consider the general principles of cooperation in the maintenance of international peace and security and may make recommendations with regard to such principles; Article 11(2) sets out a division as far as action is concerned: any such question on which action is necessary should be referred to the Security Council; Article 11(3) authorizes the General Assembly to call the (p. 20) attention of the Security Council to situations likely to endanger international peace and security.72 Article 12 is designed to avoid conflict between the two organs; it provides that while the Security Council is exercising in respect of any dispute or situation the functions assigned to it in the Charter, the General Assembly shall not make any recommendation with regard to that dispute or situation unless the Security Council so requests. That is, both the General Assembly and the Security Council may discuss questions to do with the use of force and make recommendations, but the Charter scheme empowered only the Security Council to make binding decisions on action in this area under Article 25 and it was the Security Council that was to have the primary role.73

The question therefore arises how far condemnation or approval or discussion by the Security Council and by the General Assembly are of equal importance in interpreting the Charter and developing the law on the use of force by states. Both are fora in which states can set out their legal justifications for the use of force and appeal to other states for support; accordingly it does not seem appropriate to try to distinguish between the two fora with regard to the statements in debates and in explanation of votes.74 As regards the significance of resolutions, the General Assembly may be more representative, but it was the Security Council that was expressly assigned primary responsibility for the maintenance of international peace and security. Nevertheless, the General Assembly has passed resolutions not only confirming condemnation already made by the Security Council but also condemning behaviour when a veto or threat of a veto prevented a Security Council resolution from being adopted.

At times Western powers have challenged the right of the General Assembly to use terms such as ‘aggression’ contained in Chapter VII of the UN Charter on the ground that the General Assembly should not override the discretion of the Security Council. For example, in 1981 the UK objected to the General Assembly using the phrase in relation to South Africa’s actions against the front-line states.75 Again Canada, speaking on the General Assembly resolution on the Israeli bombing of the Iraqi nuclear reactor, argued that the General Assembly should not use the term ‘acts of aggression’; it was a matter for the Security Council to make such determinations.76 The USA denounced the repeated condemnation of Israel for this attack as a ritualistic exercise which failed to make a positive contribution to (p. 21) resolving the Middle East conflict; the Security Council had itself condemned Israel for this action. Sweden opposed certain passages of General Assembly Resolution 38/180A (1983) calling for states to refrain from supplying weapons to Israel, to suspend economic and financial dealings, and to sever diplomatic, trade, and cultural links. Sweden said that these were matters for the Security Council and that the resolution could not be reconciled with the division of responsibilities between the General Assembly and the Security Council.77 That is, Western states have made it clear that they do not regard General Assembly resolutions as authoritative determinations under Chapter VII.

The assessment of Security Council and General Assembly practice may not be simple.78 After a debate member states may choose neither to pass a resolution nor to make a statement. And in their debates states are often cautious in their language; they may not always use legal language in their assessment of the justification for a use of force. They may choose rather to express sympathy or understanding of the action taken. For example, the UK, in its reaction to controversial uses of force by the USA, has from time to time adopted forms of words that allow it to offer support or sympathy but to stop short of an unequivocal endorsement of the legal argument of the USA; to a casual observer this statement may appear to offer support for the US legal argument, but in fact it does not go so far.79

The resolutions and statements of the Security Council and the resolutions of the General Assembly tend not to use the language of the Charter in Articles 2(4) and 51, nor to refer to them expressly; when they do refer to these Articles it is normally to recall them in general terms in the preamble of the resolution.80 The Security Council may not be concerned to determine legality; its role in the maintenance of international peace and security may lead it to choose to avoid any attribution of responsibility for breach of the law. Its resolutions may be indeterminate: a condemnation may be interpreted as limited to the particular facts, simply a condemnation of the particular use of force in the particular circumstances or as a pronouncement on the general law invoked by the states using force. Even when the Security Council does condemn it generally does so on the (p. 22) particular facts, in order to secure consensus and perhaps to secure the strongest condemnation possible. That is, the resolution makes no general pronouncement on the legality of, for example, anticipatory self-defence or the protection of nationals; it condemns the particular use of force. These episodes do not provide express confirmation that the general right invoked to justify the use of force is not part of international law, but if there is no example of a particular type of force escaping condemnation, that is persuasive evidence against that doctrine.

In contrast, the views expressed in the debates on the particular uses of force or in the general debates on law-making resolutions may be more revealing of states’ views of the legal position and may reflect the doctrinal divergence behind the resolutions. A resolution condemning a particular use of force may be the product of very different views of the legal position; the different states voting for the resolution may have done so for very different reasons and on the basis of different views of the law. Thus, for example, some states would reject the legality of a use of force simply because it was taken in protection of nationals abroad or was anticipatory; others would not reject all such actions in principle but would condemn the action on the particular facts because it was disproportionate or unnecessary. In the case of South Africa, Portugal, and Israel some states regarded any claim by these states to use force in self-defence against neighbouring states as defective because they were acting to further illegal policies or illegal occupation; other states accepted the possibility of self-defence by South Africa, Portugal, and Israel, but looked at each incident on its facts.

It may be argued that condemnation of a particular use of force by the Security Council or General Assembly is conclusive or at least persuasive as to illegality. Condemnation of another state by a state with whom it normally has close relations, as when the UK condemns a use of force by the USA or the USA condemns a use of force by Israel, is exceptionally strong evidence of illegality. Franck makes a convincing case with regard to the General Assembly that states tended even during the Cold War to vote in a principled way in responding to a use of force by a superpower or by a Third World state; there was not a double standard on the part of most states except for the superpowers themselves and their close supporters.81 But a slight doubt arises because occasionally both the General Assembly and the Security Council seemed willing to condemn a state for a particular episode because of its past record. Examples of this can be found in the regular condemnations of Portugal and later of South Africa for particular uses of force. It seems that because these states were acting in furtherance of colonialism and apartheid there was a readiness to condemn for individual uses of force even (p. 23) without clear evidence with regard to the particular incident. Such doubts about the evidence led Western states sometimes to abstain on certain resolutions.82

The more difficult question and one that has given rise to greater controversy among writers is whether, if condemnation is evidence of illegality, the converse is true? Is failure to condemn evidence of legality? Not necessarily so, for there are many reasons for a failure to condemn.83 Indeed, the practice of the Security Council shows a distinct reluctance to condemn; even a finding of responsibility is unusual. Even if there is an investigation of a use of force where there are conflicting claims by the two sides there may be no conclusion as to responsibility and no blame.84 Similarly the UN Secretary-General, in his many reports on conflicts to the Security Council, generally avoids the attribution of responsibility unless expressly asked to pronounce on this, as, for example, when the Security Council asked him to report on the responsibility for the start of the Iran/Iraq war in 1980.85 He is generally very careful in his public statements not to attribute blame for breach of the law on the use of force. It is also common for the Security Council and the General Assembly’s initial response to a conflict to be to avoid any finding of responsibility and simply to call for an end to all intervention.

Thus the Security Council unanimously passed Resolution 479 (1980) at the outbreak of the Iran/Iraq conflict; this called upon Iran and Iraq to refrain immediately from any further use of force and to settle their dispute by peaceful means. The resurgence of conflict in Kashmir and the outbreak of conflict between Ethiopia and Eritrea led the Security Council again simply to call for peaceful settlement. With regard to the latter conflict, the Security Council subsequently imposed an arms embargo on both states in Resolution 1298 (2000). In contrast the Security Council did not call for an immediate ceasefire when Israel invaded Lebanon and when Ethiopia invaded Somalia in 2006. Express findings of aggression (or of aggressive acts) are extremely unusual. It has only been states that were in some sense seen as outlaws which have been condemned for aggression by both the Security Council and the General Assembly; Portugal (p. 24) when it refused to relinquish its colonial possessions, Southern Rhodesia after its unilateral declaration of independence, Israel after its occupation of the West Bank, Gaza, and other territory, South Africa during apartheid and its occupation of Namibia, Indonesia after its invasion of East Timor, and Iraq after its invasion of Kuwait. Express condemnation by name is also unusual, and Security Council Resolution 1862 (2009) recalling its condemnation of Eritrea’s military action against Djibouti is exceptional. It may nevertheless be clear which state is being criticized. For example, in 1983 the General Assembly passed Resolution 38/10 on Central America by consensus; it asserted in general terms the duty of all states to refrain from the threat of use of force, and the inalienable right of all peoples to decide on their own form of government free from all foreign intervention, coercion, or limitation; it then condemned the acts of aggression against the sovereignty, independence, and territorial integrity of the states of the region, but did not name any specific state as responsible.86 Similarly when Turkey invaded Cyprus, Iran attacked commercial shipping during the Iran/Iraq war, the USA intervened in Grenada and Nicaragua, resolutions passed by the Security Council and the General Assembly condemned the behaviour, but did not name the state responsible.

If there is no condemnation of a particular use of force by the Security Council because a permanent member actually uses its veto, or threatens to use its veto, it would seem to be even harder to argue that the use of force is therefore legal.87 A few writers have, however, made this argument and have asserted that failure of the Security Council to condemn (whether because of the veto or not) constitutes acquiescence by other states and helps to undermine the prohibition on the use of force or intervention and to support controversial doctrines of international law, such as a right of pro-democratic intervention or the (pre-9/11) right to use force in retaliation for terrorist attacks or the right to use force to protect nationals abroad.88 This unusual approach to the assessment of state practice discounts the statements of states and ignores widespread condemnation; it also discounts not only general resolutions of the General Assembly on the use of force but also the massive network of treaties which reinforce the prohibitions of the use of force and of intervention; it gives decisive weight to the action of the state using force. This clearly privileges powerful states and especially the permanent members of the Security Council who, through the veto or threat of veto, can according to (p. 25) this doctrine create new customary international law in reinterpretation of the Charter. In a more extreme version of this argument, some have argued that even Security Council or General Assembly condemnation of a particular use of force, if it is not followed by any action against the state condemned, also constitutes acquiescence.89 Some, like D’Amato, have used these arguments mainly to argue that controversial US actions are lawful; others have applied it to challenge the customary status of the prohibition on force.90 Both these approaches discount what states say in reaction to the use of force by other states; they claim that the absence of a Security Council or General Assembly resolution or of any sanctions against the state using force means that its behaviour should be seen not as a breach of international law but as the emergence of a new right to use force.

The effect of this argument is compounded by the fact that some of these writers also discount what the states using force actually say in justification of their use of force and try to extract new rights to use force on the basis of the actions of the states using force. That is, they ignore the fact that states generally do not claim revolutionary new rights to use force, but try to defend their use of force by claiming self-defence or other legal justifications. They say that the state practice should be reinterpreted in the light of what the state could or should have said to explain its actions. Thus, if the action could be favourably described as humanitarian intervention, or pro-democratic intervention, then this supports the emergence of such a doctrine, even though states do not invoke these new rights but base their use of force on traditional doctrines. The Court in the Nicaragua case refused to take this approach in its consideration of the question whether a new customary law right of forcible intervention to assist opposition forces to overthrow governments had become established. For the Court, the fact that states did not claim a new right of intervention was a decisive factor in the rejection of the emergence of any new customary law right. States in fact justified their interventions by invoking the doctrine of collective self-defence; they did not claim a new right to use force in response to invitations from opposition forces.91

Clearly there can be no common ground in the assessment of the significance of state practice between those writers who discount what states say and those who take the more traditional view adopted by the ICJ in the Nicaragua case.92 It is (p. 26) only a few writers who take this extreme position of treating General Assembly or Security Council condemnation as support and ignoring the actual language of states. This approach has been subjected to serious criticism,93 but it cannot be ignored because with regard to Kosovo (1999) there were signs that some states were putting forward such arguments in their attempt to justify the NATO action. That is, they were arguing that past practice should be reinterpreted to support a doctrine of humanitarian intervention. Former US State Department Legal Adviser Harold Koh also took this approach with regard to Syria.94

Effectiveness of the Prohibition of the Use of Force

The question as to how far divergences from the prohibition on the use of force should be seen not as breaches but rather as exceptions to or modifications of the prohibition is crucial also to any assessment of the role of international law in this area. There is widespread scepticism as to the ‘effectiveness’ of international law on the use of force, intensified by Operation Iraqi Freedom (2003), and the recent interventions in Libya, Syria, Ukraine, and Yemen. Is this scepticism justified? The gap between the prohibition of the use of force and the practice seems striking to some commentators, but this divergence should not necessarily be taken as proving the ineffectiveness or pointlessness of the law in this area. Conversely, international law should not be assumed to be effective in the sense of controlling or influencing state behaviour just because state behaviour is in fact in compliance with it.

As the ICJ put it in the Nicaragua case, in a now very well-known passage in its discussion of whether the prohibition of the use of force does represent customary international law:

It is not to be expected that in the practice of States the application of the rules in question should have been perfect, in the sense that States should have refrained, with complete consistency, from the use of force or from intervention in each other’s internal affairs. The Court does not consider that, for a rule to be established as customary, the corresponding practice must be in absolutely rigorous conformity with the rule. In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of States should, in general, be consistent with such rules, and that instances of State conduct inconsistent with a given rule should generally be treated as breaches of that rule, not as indications of the recognition (p. 27) of a new rule. If a State acts in a way prima facie incompatible with a recognized rule, but defends its conduct by appealing to exceptions or justifications contained within the rule itself, then whether or not the State’s conduct is in fact justifiable on that basis, the significance of that attitude is to confirm rather than to weaken the rule.95

But the insistence that breaches may be seen as strengthening rather than negating rules cannot be taken too far without losing plausibility.

In this as in other areas, it is fundamentally misguided to attribute to international law an exclusive role in controlling state behaviour; it tends to be non-lawyers rather than lawyers whose expectations are unreasonably elevated and who attack international law as having no significant role when there is anything less than perfect compliance. As in the national sphere, legal rules are only one among a variety of factors that may influence behaviour.

Questions as to whether international law does influence state behaviour involve a study of the role of international law in national decision-making; this requires empirical work on the internal decision-making processes. The focus must shift from the artificial legal entity, the state, to the politicians and officials actually making the decisions on the use of force and the response to the use of force by others. But there are all sorts of practical problems with this type of empirical work. A state is not a unitary entity; there may be a wide range of views, even diametrically opposed views, as to the content and importance of international law on the use of force within the branches of government or between those branches. This was very striking in the administration of President George W Bush where it appeared that different members of the administration deliberately expressed contradictory positions on international law. Insofar as an investigation of the role of international law in decision-making rests on self-reporting by those involved, there is a danger that it will not give an accurate picture.96 Access to the material on national decision-making may be possible only many years after the events in question. Studies such as that of Chayes on the 1962 Cuban Missile Crisis remain unusual.97 Thus the role of the law in the UK decision-making process in the 1956 Suez Crisis came to light only thirty years later when the official papers could finally be published.98 The Report of the Chilcot Inquiry into the UK’s role in the 2003 Iraq War is exceptional in its detailed examination of the decision-making process.99 It discloses the different views on the legality of the use of force put forward by the Attorney-General, the Foreign Office legal advisers in London and (p. 28) at the UN, and the Foreign Secretary. It reveals the Prime Minister’s reluctance to request formal legal advice when it was clear that the advice would not support his determination to use force, and the change of mind by the Attorney-General as to the legality of military intervention.

Moreover, generalization may not be justified; just because the officials and politicians used international law in one way in one episode it does not follow that the same approach would be adopted in different circumstances. That is, the question of the impact of international law on national decision-making is not easily resolved, if at all. In the absence of such empirical research the matter remains one for inference from public statements and actions of states. Simple conclusions as to effectiveness may not be possible. Some have argued that the prohibition on the use of force is not customary law because states had used force both before and after the Charter and the reactions of other states were often ambiguous and inadequate.100 Others say that, broadly, states comply with the law outlawing the use of force.

One of the issues that has given rise to the most significant scepticism as to effectiveness of the prohibition of the use of force is the question as to whether breach of the law on the use of force is cost-free, whether states may break the law and get away with. This question also is not susceptible of a simple answer. The UN collective security system was generally incapacitated during the Cold War, although regional organizations did impose sanctions in some cases.101 It is notorious that the only use of Chapter VII enforcement action involving armed force was in Korea, and the legal status of even that action was controversial. The only uses of UN economic sanctions were against Southern Rhodesia and South Africa. The Security Council and the General Assembly from time to time issued condemnations of the use of force by states in their resolutions. The question as to how far a simple condemnation by the Security Council or the General Assembly or a regional organization operated as a disincentive, even in the absence of any formal collective sanction, is not a simple one. Again there can be no conclusive answer without looking behind the state facade, but it is clear from public information that states argue and negotiate to try to avoid condemnation; the price may be intangible, but it is one that states using force do not want to have to pay. The set-piece Security Council and General Assembly debates in which they repeated year after year their condemnation of earlier uses of force by certain states fulfilled a symbolic role.102 Thus year after year the General Assembly (p. 29) voted to condemn the Israeli attack on the Iraqi nuclear reactor, Vietnam’s intervention in Cambodia, and the USSR invasion of Afghanistan.103 Of course, a hazard of this practice is that the General Assembly is then trapped into continuing, because to stop could give the message that the behaviour is somehow now accepted.

The rules of international law in this area clearly also serve a declaratory function; they set out the goal to be aimed at, the ideal that states adhere to. This symbolic function is apparent in the 1986 African Charter on Human and Peoples’ Rights, the UN General Assembly’s 1984 Declaration on the Right of Peoples to Peace, and 2016 Declaration on the Right to Peace when they assert the right of peoples and individuals to national and international peace and security.104 Many resolutions of the UN General Assembly have been passed to reassert and develop the rules in the Charter. As was explained above, typically the Western states have been suspicious of such resolutions and their ritual reaffirmation of existing rules. They have seen them as pointless and/or dangerous, pointless in that they add nothing to the UN Charter and dangerous insofar as they may depart from it. It is easy to be cynical about such resolutions, especially when they were advocated by states such as the USSR, contemporaneously involved in aggression against others. China and Albania both regarded the proposal for the 1987 Declaration on the Non-Use of Force as a fraudulent abuse. Much of the debate over the 1987 Declaration was taken up by political point-scoring about breaches of the general rules that states were solemnly debating. But small and new states typically have supported the drafting of general resolutions on the use of force. They have been willing to seek consensus and not simply to use their majority in the General Assembly. Some of the suspicion of general statements of principle misses the point that many states were still colonies at the time of the adoption of the Charter by the fifty-one original member states and that they had come to want to take part in the public reaffirmation of its most important rules. Moreover, the drafting of substantive rules has from the start been accompanied by concern over the functioning of the UN system. To accompany the general resolutions on the use of force the General Assembly has worked endlessly, and often on the initiative of the Western states, on resolutions with a more practical focus, such as the Declaration on the Strengthening of International Security, and on Questions concerning the UN Charter and the Strengthening of the Role of the UN, Good Neighbourliness, and so on.

Given the problems of any empirical investigation into ‘effectiveness’, it is all the more important to look at international law on the use of force in terms of the language used by states. Given that in fact they choose to use this language to (p. 30) explain their behaviour and to respond to that of others, anyone involved in any way in advising states or in assessing their actions will have to be able to engage in this discourse. Simple assertions that this use of language is mere cynical manipulation of the rules, and no more than ex post facto rationalization for actions reached on other grounds, are not justified in the absence of empirical evidence that this is in fact the case, and such assertions are no more plausible than the opposite version that states are in fact influenced by law. Of course, it is common for states to offer other justifications as well; it is rare for a state to use the language of international law exclusively. They also offer political explanations, criticisms, and justifications, but with only a tiny number of exceptions they take care to offer a legal argument for their use of force. It is very rare for them not even to try to provide a legal justification. The UK, in response to domestic pressure, gave an elaborate legal justification for its participation in Operation Iraqi Freedom. The USA, unconstrained by comparable domestic pressure, was nevertheless concerned to build international support for a mixture of practical and political reasons, and it also offered a legal argument, even if this was not set out in any great detail until after the event.105 President Trump has not to date set out legal justifications for the USA’s 2017 direct intervention in Syria at any length; he seems to be relying on doctrines developed by the previous administration to explain his escalation of the use of force. It remains to be seen whether this will continue.

The rare instances when states seem to have made a deliberate decision not to give a legal explanation stand out. The absence of any real attempt at a legal justification by the USA, the UK, and France for the protection of the Kurds in 1991 and by Turkey for its incursions into Iraq in pursuit of the PKK since the 1990s is unusual and seems to indicate considerable doubt as to the legality of these actions.106 Israel offered no legal justification for its repeated incursions into Syria against Hezbollah since 2011.107 Even when politicians do occasionally say that they will no longer observe international law restrictions on the use of force, as was sometimes the case during the Reagan era when the administration suggested that it was not necessary to comply with international law in response to an enemy, an evil empire that did not itself observe the law, the USA continued (p. 31) to offer legal argument in the Security Council.108 Rather than not even attempt a legal justification, commonly states offer what may seem weak or unconvincing arguments. But it is always important to allow for different viewpoints; even when two opposing states both invoke self-defence they may both believe they have right on their side. Often it is a series of arguments that are offered, maybe differing over time, in order, or emphasis. This combination of a series of different justifications is typical legal reasoning, often apparent in arguments in court; a whole series of arguments of differing strengths is included on the chance that one of them may appeal to one particular audience. During the Cold War a constraint on this rhetoric was the consideration that the language of states in their interpretation and application of the UN Charter could operate as a precedent and later be invoked against them.109 The end of the Cold War has apparently weakened this constraint, at any rate as far as the USA is concerned. The crucial question is whether other states now feel emboldened by the USA’s flexible approach to the Charter provisions themselves to pursue military solutions to problems better solved by the slow and difficult path of diplomacy. Perhaps instead of asking about the effectiveness of the law on the use of force we should ask about the effectiveness of the use of force: does the use of force achieve the aims of the state or is it ineffective or even counter-productive.110 If reliance on a wide right of self-defence does not make a state more secure, and if humanitarian intervention cannot secure an improvement in the situation of the people on the ground, then it is open to question whether military action is lawful.


1  On the positive side a settlement was reached with Iran over its nuclear programme, SC Res 2231 (2015), though Israel and Saudi Arabia opposed the settlement, and the USA under President Trump is also critical. The long-lasting internal conflict in Colombia between the government and the FARC has come to an end, SC Res 2261 (2016). In Sri Lanka the government defeated the Tamil Tigers in their prolonged armed struggle for autonomy (2009).

2  Several long-lasting conflicts continue, some dating back to the establishment of the UN. Among the first conflicts ever considered by the Security Council were those between India and Pakistan and between Israel and Arab states. These disputes have continued off and on for the last sixty years and are to a large extent still unresolved. There is no sign of progress towards a two-state solution to the Israel/Palestine problem. In Kashmir, clashes between India and Pakistan in the last two years show that there is still a possibility of conflict between these two nuclear-weapon states. Long-lasting civil wars and separatist struggles also continue in Burma, Indonesia, the Philippines, and Thailand. Ethiopia still occupies territory belonging to Eritrea and the bad relations between the two states have had repercussions for Somalia and Djibouti. In Mexico, drug-related violence, produced by the unwinnable ‘war on drugs’, reached new levels in 2017.

3  It referred to arguments used by Western states with regard to their military interventions in Kosovo (1999), Iraq (2003); see Gray, ‘The War in Georgia’, in Corten and Ruys (eds), The Use of Force in International Law—a Case-based Approach (2018), Chapter 54.

4  See discussion in Chapter 3.

5  States without effective governments may not be able to prevent the trafficking of migrants, drugs, and small arms, and they offer freedom for terrorists to operate.

6  Its origins lay in Iraq, as Al Qaida in Iraq, where its strength grew in Sunni areas following Operation Iraqi Freedom (2003). The conflict in Syria meant that it could now operate across borders, and it proclaimed a new cross-border caliphate in 2014. The group is variously referred to as Islamic State of Iraq and Syria, Islamic State of Iraq and the Levant, Islamic State and Daesh. For convenience it will be referred to as ISIS in this book. Its adherents include groups in the Philippines, South Thailand, and Boko Haram in Nigeria. See Secretary-General’s Reports UN docs S/2016/92, S/2016/501, S/2016/830, S/2017/97, S/2017/467.

7  UK Materials on International Law, 72 BYIL (2001) 690, 697; Bellinger, US State Department Legal Advisor, <www.opiniojuris.org/posts/1168811565.shtml>. See also, Greenwood, ‘War, Terrorism and International Law’, 56 Current Legal Problems (2003) 505; Duffy, The War on Terror (2nd edn 2015).

8  For criticism of the use of the language of ‘war’, see Megret, ‘War? Legal Semantics and the Move to Violence’, 13 EJIL (2002) 361. For an opposing view, see Dinstein, War, Aggression and Self-Defence (5th edn 2011); Dinstein argues throughout his book for a wide and very controversial concept of the state of war. For an early critique of the strategy of the ‘global war on terrorism’, see Record, Bounding the Global War on Terrorism (2003), arguing that ‘The Global War on Terrorism as it has so far been defined and conducted is strategically unfocused, promises much more than it can deliver, and threatens to dissipate scarce US military and other means over too many ends. It violates the fundamental strategic principles of discrimination and concentration.’

9  Thus President George W Bush and PM Blair linked diverse groups of terrorists as all part of the same global threat.

10  Secretary-General’s Address to the General Assembly, 23 Sept 2003; Secretary-General’s Message for the New Year, 2004, UN Press Release SG/SM/9095, 24 Dec 2003.

11  The High-level Panel on Threats, Challenges and Change mandated to make a broad examination of global peace and security issues, to identify the contributions of collective action in addressing major challenges and threats, and to recommend changes necessary to ensure effective collective action issued its report A More Secure World in 2004, UN doc A/59/565. In 2005 the Secretary-General issued his own report, In Larger Freedom, UN doc A/59/2005. See 11JCSL (2006) 107 for a workshop on these reports. Finally the 2005 World Summit produced an Outcome document, UN doc A/60/L.70. See Gray, ‘A crisis of legitimacy for the UN collective security system?’, 56 ICLQ (2007) 157.

12  UN doc A/59/565 para 192, 198; UN doc A/59/2005 para 126, 153; UN doc A/60/L.70 para 79.

13  Report on the Legal and Policy Frameworks guiding the United States’ Use of Military Force and Related National Security Operations, Dec 2016 <https://fas.org/man/eprint/frameworks.pdf>.

14  See Chapter 5 on the controversies about the scope of self-defence.

15  Franck, ‘What happens now? The UN after Iraq’, 97 AJIL (2003) 607. Franck had already asked ‘Who killed Article 2(4)?’, 64 AJIL (1970) 809.

16  Glennon, Limits of Law, Prerogatives of Power: Interventionism after Kosovo (2001); ‘The Fog of Law: Self-Defense, Inherence and Incoherence in Article 51 of the UN Charter’, 25 Harvard Journal of Law and Public Policy (2002) 539; ‘The emerging use of force paradigm’, JCSL (2006) 309; Bolton, ‘Is there really “Law” in International Affairs?’, 10 Transnational Journal of Law and Contemporary Problems (2000) 1.

17  Wedgwood, ‘The Fall of Saddam Hussein: Security Council mandates and pre-emptive self-defense’, 97 AJIL (2003) 576; Stromseth, ‘Law and Force after Iraq—A Transitional Moment’, 97 AJIL (2003) 628; Yoo, ‘Using Force’ 71 U Chic LR (2004) 729.

18  See, for example, Byers and Nolte (eds), United States Hegemony and the Foundations of International Law (2003); Vagts, ‘Hegemonic International Law’, 95 AJIL (2001) 843; Farer, ‘The Prospect for International Law and Order in the Wake of Iraq’, 97 AJIL (2003); Franck, ‘The power of legitimacy and the legitimacy of power’, 100 AJIL (2006) 88; Krisch, ‘International Law in Times of Hegemony’, 16 EJIL (2005) 368.

19  UN Operation in Côte d’Ivoire (UNOCI) has come to a successful conclusion; UN Stabilization Mission in Haiti (MINUSTAH) has been transformed into a non-military force after thirteen years; and UN/AU Hybrid Operation in Darfur (UNAMID) was reduced in size because of the improved security situation.

20  The Trump administration has put pressure on the UN to cut the costs of peacekeeping,  <https://www.nytimes.com/2017/03/24/world/united-nations-peacekeeping-trump-administration.html>.

21  SC Res 2147 (2014).

22  See Chapter 6 for further discussion of this report.

23  For an authoritative account of the history of international law on the use of force, see Brownlie, International Law and the Use of Force by States (1963), and also Verdebout, ‘The contemporary discourse on the use of force in the 19th century’, 1 Journal on the Use of Force and International Law (2014) 223.

24  Article 2(4): ‘All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.’

25  See, for example, the debate between Bowett, Self-Defence in International Law (1958) and Brownlie, note 23 above.

26  Article 51: ‘Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.’

27  Greenwood, ‘The concept of war in modern international law’, 36 ICLQ (1987) 283.

28  The lack of any express correlation between the terms used in Articles 2(4) (‘use of force’), 51 (‘armed attack’), and 39 (‘act of aggression’) contributes to the uncertainty.

29  On the challenges to this view, see discussion in Chapters 2 and 5.

30  See Human Security Report 2005, War and Peace in the Twenty-first Century (2005) and the more recent surveys in the SIPRI Yearbook and PRIO, Trends in Armed Conflict 1946–2014.

31  Ford, ‘Legal Processes of Change: Article 2(4) and the Vienna Convention on the Law of Treaties’, 4 Journal of Armed Conflict Law (1999) 75; Kammerhofer, ‘The resilience of the restrictive rules on self-defence’, in Weller (ed), The Oxford Handbook of the Use of Force in International Law (2015) 627.

32  See discussion by Corten, ‘The controversies over the customary prohibition on the use of force’, 16 EJIL (2005) 803; Banks and Criddle, ‘Customary Constraints on the Use of Force: Article 51 with an American accent’, 29 Leiden JIL (2016) 67; van Steenberghe, ‘The Law of Self-defence and the New Argumentative Landscape on the Expansionists’ Side’, ibid, 43.

33  See, for example, UN doc S/2014/573, and the Final Declaration of the 17th NAM Summit <www8.irna.ir/en/News/82235410/>.

34  Not surprisingly former US State Department Legal Adviser, Harold Koh, and Former UK FCO Legal Adviser, Daniel Bethlehem, take this approach in their writing on the use of force. See, for example, Bethlehem, ‘Self-defence against non-state actors’, 106 AJIL (2012) 769, and replies by Glennon, O’Connell, Tladi, and Wilmshurst.

35  This type of approach is especially apparent with regard to the US invocation of a wide right of self-defence in Syria. See Chapter 5.

36  See, for example, Corten, The Law against War (2011), and Le droit contre la guerre (2nd edn 2014); Ruys, Armed Attack and Article 51 of the UN Charter (2010); van Steenberghe, La légitime défense en droit international public (2012).

37  See, for example, the conflicting views on the interpretation of Article 2(4) based on the same practice: Corten, note 36 above, and Ruys, ‘The meaning of force and the boundaries of the Jus ad Bellum’, 108 AJIL (2014) 159.

38  Case Concerning Military and Paramilitary Activities in and against Nicaragua (hereafter Nicaragua case) ICJ Reports (1986) 14 at para 176.

39  The Court’s approach to customary international law in the Nicaragua case, at para 183, was traditional; it stressed the need for practice and opinio juris and made clear that universal compliance was not necessary. The Court was much criticized, not so much for this traditional doctrine, but for its application of it in the pursuit of the rules of international law. It was criticized for not undertaking a wide survey of practice, and for inferring opinio juris from General Assembly resolutions. But, as the Court said, the parties were in agreement that Article 2(4) was customary law. It is therefore not surprising that the Court’s inquiry into customary international law was relatively brief.

40  See Gray, ‘The Principle of Non-Use of Force’, in Lowe and Warbrick (eds), The United Nations and the Principle of International Law (1994), 33.

41  GA Res 3314 (1974).

42  GA Res 2625 (1970).

43  GA Res 42/22 (1988); see Treves, ‘La Déclaration des Nations Unies sur le renforcement de l’efficacité du principe du non-recours à la force’, 33 AFDI (1987) 379.

44  Nicaragua case para 188; Legality of the Threat or Use of Nuclear Weapons, ICJ Reports (1996) 226 at para 70.

45  Though there are problems in assessing the question how far what states say in these debates is significant. They may change their views; clearly their views at any particular time are influenced by the disputes in which they are directly involved or in which they are interested. Typically states may attack each other and set out their own justifications for force during the general debates; during the drafting of the Declaration on the Non-Use of Force Iran and Iraq, Cyprus and Turkey, and the Arab states and Israel all criticized each other. It is important to see the statements in the context of the time in which they were made. Views expressed in debates on the adoption of declarations may be modified later in response to particular conflicts. Thus the former Soviet bloc at first opposed the inclusion of indirect aggression in aggression and armed attack, but later apparently abandoned this view with regard to Czechoslovakia and Afghanistan.

46  UN doc A/72326; see Treves, note 43 above; Gray, note 40 above.

47  The issues of economic blockade of landlocked states and environmental modification also emerged. The remaining differences between developed and developing states are summarized at UN doc A/40/41.

48  Doswald-Beck, ‘The Legal Validity of Military Intervention by Invitation of the Government’, 56 BYIL (1985) 189; see Chapter 3.

49  See Chapter 3.

50  Higgins, The Development of International Law through the Political Organs of the United Nations (1963) at 181.

51  This covered events in 1948–9 on the Costa Rica border, and between Haiti/Dominican Republic; in 1950, Dominican Republic allegations against groups in Cuba and Guatemala; in 1954, Guatemala; in 1955, Costa Rica. At this time there was a serious debate as to priority of jurisdiction between the UN and regional organizations, but this has not been such a controversial issue in recent years: Simma et al. (eds), The United Nations Charter: A Commentary (3rd edn 2012) at 1429. The UN SC Annual Reports to the General Assembly now once more provide this information on matters brought to the attention of the SC but not discussed by it.

52  For example, 1978 UNYB 5.

53  There is also controversy as to the significance of its statements, as opposed to its resolutions: see Talmon, ‘The statements by the President of the Security Council’, 2 Chinese JIL (2003) 419.

54  Brownlie, ‘The Decisions of the Political Organs of the UN and the Rule of Law’, in Macdonald (ed), Essays in Honour of Wang Tieya (1994), 91; Caron, ‘The Legitimacy of the Collective Authority of the Security Council’, 87 AJIL (1993) 552; Bedjaoui, The New World Order and the Security Council: Testing the Legality of its Acts (1994); Dossier: Actualité de Pouvoirs du Conseil de securité, 37 Revue Belge de droit international (2004) 457; de Wet, The Chapter VII Powers of the UN Security Council (2004); see also Chapter 6.

55  Thus in the Lockerbie case Libya argued that a Security Council resolution was invalid because the Security Council was not entitled to find a threat to the peace under Article 39 such as to justify it in passing a binding resolution under Chapter VII, Cases concerning Questions of Interpretation and Application of the 1971 Montreal Convention arising from the Aerial Incident at Lockerbie, Preliminary Objections, Libya v UK, Libya v USA, ICJ Reports (1998) 9, 115. In Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Provisional Measures) ICJ Reports (1993) 3, 325 the Court was asked to pronounce on the validity of the Security Council arms embargo on the whole of the former Yugoslavia imposed in Security Council Resolution 713 (1991), and to determine whether the embargo was invalid because it conflicted with the right of self-defence of Bosnia-Herzegovina under the UN Charter.

56  Gowlland-Debbas, ‘The Relationship between the International Court of Justice and the Security Council in the Light of the Lockerbie case’, 88 AJIL (1994) 643; Graefrath, ‘Leaving to the Court what belongs to the Court’, 4 EJIL (1993) 184; Franck, ‘The Powers of Appreciation: Who is the Ultimate Guardian of UN Legality’, 86 AJIL (1992) 519; Alvarez, ‘Judging the Security Council’, 90 AJIL (1996) 1; Gray, ‘The Use and Abuse of the International Court of Justice: Cases concerning the Use of Force after Nicaragua’, 14 EJIL (2003) 867, and ‘The ICJ and the Ius ad Bellum’ in Tams and Sloan (eds), The Development of International Law by the ICJ (2013) 237.

57  Nicaragua case, (Jurisdiction and Admissibility) ICJ Reports (1984), 392 at para 98.

58  In 1998 the Court found jurisdiction (ICJ Reports (1998) 275; it gave judgment on the merits in 2002.

59  The Court found jurisdiction in ICJ Reports (1996) 803, and gave judgment on the merits in 2003.

60  The Case concerning the Aerial Incident of 3rd July, 1988 was settled: 35 ILM (1996) 550.

61  Legality of the Use of Force, Yugoslavia v Belgium, ICJ Reports (1999) 124. The Court refused provisional measures on the basis that it lacked prima facie jurisdiction on the merits of the case: see Chapter 2.

62  Aerial Incident of 10 August 1999 (Pakistan v India).The Court decided that it had no jurisdiction to decide this case: ICJ Reports (2000) 12.

63  Armed Activities on the Territory of the Congo (DRC v Uganda) ICJ Reports (2005) 168. The DRC withdrew the cases against Burundi and Rwanda, but later brought a new case against Rwanda in 2002. The Court held it had no jurisdiction in this case: ICJ Reports (2006) 6.

64  ICJ Reports (2002) 303 para 308.

65  ICJ Reports (2015) 665 para 97.

66  ICJ Reports (2016) para 76.

67  ICJ Reports (2003) 161. See Chapter 4. For a discussion of the Court’s controversial assertion of its jurisdiction to consider this issue, see Chevenier, ‘Oil on Troubled Waters’, 63 CLJ (2004) 1. Several judges (including Judges Elaraby, Simma, and Rigaux) were apparently influenced by the need to reaffirm the law on the use of force in the light of Operation Iraqi Freedom.

68  ICJ Reports (2005) 168. It avoided pronouncing on the question whether Uganda’s acts amounted to aggression.

69  See Gray, note 56 above. Commentators who support a wide right of self-defence tend to dismiss the Court’s judgments as outdated or misguided.

70  It avoided giving judgment in the two Nuclear Tests cases (ICJ Reports (1974) 253, 457) and rejected New Zealand’s attempt to reopen this case in 1995 (ICJ Reports (1995) 288). It refused the WHO’s request for an Advisory Opinion (AO) on nuclear weapons (ICJ Reports (1996) 66). It did give an AO requested by the UN GA on the Legality of the Threat or Use of Nuclear Weapons, but notoriously avoided a clear answer in the central part of its opinion, ICJ Reports (1996) 226. In 2016 the ICJ rejected jurisdiction in the cases brought by the Marshall Islands against the UK, India, and Pakistan.

71  White, ‘The relationship between the UNSC and GA in matters of international peace and security’, in Weller, note 31 above, at 293.

72  Simma et al. (eds), The UN Charter: A Commentary (3rd edn 2012) at 491. On the drafting history of Articles 10–13, see also Franck, Recourse to Force (2002) at 31.

73  This question arose recently in the AO on Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, ICJ Reports (2004) 136 para 25. See Chapter 6. On the question of which Security Council resolutions are binding, see Sievers and Daws, The Procedure of the UN Security Council (4th edn 2014), Chapter 6.

74  See White, note 71 above.

75  1981 UNYB 228.

76  1982 UNYB 425.

77  1983 UNYB 330. In the vote on GA Res 36/27 (109-2-34) condemning Israel for its attack several Western states abstained on this ground.

78  See Franck, Recourse to Force (2002), for an examination of Security Council practice. Franck argues that the actual practice of UN organs manifests ‘a situational ethic rather than doctrinaire consistency’ on self-defence and other subjects. His study leads him to conclude that certain ‘unconventional justification [for the use of force] has been validated in systemic practice’. However, to the extent that he is arguing that failure by states to condemn certain controversial behaviour may lead to a change in the law and the acceptance of loopholes in the Charter allowing anticipatory self-defence and humanitarian intervention, the inferences he draws from practice are open to question: see 24 below.

79  Unfortunately commentators do not always pick up such nuances in the language.

80  The Repertoire of Practice of the Security Council and the Repertoire of Practice of UN Organs list such express references.

81  Franck, ‘Of Gnats and Camels: Is there a Double Standard at the United Nations?’, 78 AJIL (1984) 811.

82  Such doubts led Western states sometimes to abstain on certain resolutions, see 1969 UNYB 137; 1969 UNYB 140; 1976 UNYB 166.

83  See Barsotti, ‘Armed Reprisals’, in Cassese (ed), Current Legal Regulation of the Use of Force (1986), 79. For example, states on the Security Council or the General Assembly may think that, although the legality of a particular use of force is open to question, the acts should not be condemned because they were morally or politically justified. (As, for example, with the failure to condemn Israel in 1967 over the Entebbe raid, the Tanzanian invasion of Uganda to overthrow Idi Amin, or the split vote on the condemnation of the US use of force against Panama.) For a recent exposition of the view that failure to condemn, or failure expressly to reject a particular legal justification, amounts to approval, see Steenberghe, ‘Self-defence in response to attacks by non-state actors’, 23 Leiden JIL (2010) 183; ‘The law against war or Jus contra Bellum?’, 24 Leiden JIL (2011) 747.

84  As with Iran/Iraq in 1974, 1974 UNYB 252.

85  UN doc S/23273, 9 December 1991.

86  1983 UNYB 197.

87  The US government took this position with regard to regional action under Chapter VIII; failure to condemn was argued to constitute authorization by the Security Council: see Chapter 8.

88  D’Amato, International Law: Process and Prospect (2nd edn 1995), Chapter 6; and also 108 AJIL (2014) 650 for a reaffirmation of his approach and replies; Weisburd, Use of Force (1997); Arend and Beck, International Law and the Use of Force (1993), Chapter 10. Franck takes a similar line in Recourse to Force (2002). On pro-democratic invasions, see Chapter 2; on force against terrorist attacks and the protection of nationals, see Chapters 4 and 5.

89  Weisburd, ibid; Arend and Beck, ibid.

90  Arangio-Ruiz, The UN Declaration on Friendly Relations and the System of Sources of International Law (1979). Franck, ‘Who killed Article 2(4)?’, 64 AJIL (1970) 809, and reply by Schacter, ‘The Reports of the Death of Article 2(4) are Greatly Exaggerated’, 65 AJIL (1971) 544; Franck, Recourse to Force (2002).

91  Nicaragua case, para 207.

92  Farer, ‘Human Rights in Law’s Empire: The Jurisprudence War’, 85 AJIL (1991) 117; Franck, Recourse to Force (2002); Murphy, ‘The doctrine of preemptive self-defense’, 50 Villanova LR (2005) 699 at 727; Corten, ‘The controversies over the customary prohibition on the use of force’, 16 EJIL (2005) 803.

93  Mullerson, ‘Sources of International Law: New Tendencies in Soviet Thinking’, 83 AJIL (1989) 494 at 505; Brownlie, ‘The UN Charter and the Use of Force 1945–1985’, in Cassese (ed), The Current Legal Regulation of the Use of Force (1986) at 491. Akehurst, ‘Letter’, 80 AJIL (1986) 147.

94  Koh, ‘Syria and the law of humanitarian intervention’, <www.ejiltalk.org/Syria-and-the-law-of-humanitarian-intervention-part-ii-international-law-and-the-way-forward/>. For further discussion on Kosovo and Syria, see Chapter 2.

95  Nicaragua case, para 186.

96  See Scharf, ‘International law in crisis: a qualitative empirical contribution to the compliance debate’, 31 Cardozo LR (2009) 45. See also Bolton, Surrender is not an Option (2007) for a sceptical approach.

97  Chayes, The Cuban Missile Crisis (1987).

98  Marston, ‘Armed Intervention in the 1956 Suez Canal Crisis’, 37 ICLQ (1988) 773.

100  Arangio-Ruiz, The UN Declaration on Friendly Relations and the System of Sources of International Law (1979); Glennon, Limits of Law, Prerogatives of Power: Interventionism after Kosovo (2001).

101  See Chapter 8.

102  Bleicher, ‘The Legal Significance of Recitation of General Assembly Resolutions’, 63 AJIL (1969) 444; Sloan, ‘General Assembly Resolutions Revisited’, 58 BYIL (1987) 41.

103  It is interesting that after Iraq invaded Kuwait in 1990 the ritual inclusion of the Israeli attack on Iraq’s nuclear reactor was dropped.

104  UN GA Res 39/11, Res 32/28.

105  Taft and Buchwald, Legal Adviser and Assistant Legal Adviser, US State Department, ‘Pre-emption, Iraq and International Law’, 97 AJIL (2003) 557.

106  On the protection of the Kurds in Iraq, see Chapter 2; on Turkey’s incursions into Iraq, see Chapter 4. On the failure of Turkey to offer reasoned legal justification for its use of force in the 1990s, see Gray and Olleson, ‘The Limits of the Law on the Use of Force: Turkey, Iraq and the Kurds’, 12 Finnish YBIL (2001) 355.

107  Nor did Israel acknowledge or defend its use of force against Syrian government sites (allegedly linked to the production of chemical weapons) in September 2017, Loveluck and Morris, ‘Israeli airstrike targets Syrian military site as tensions rise’, 7 Sept 2017. States generally do not offer legal justifications for the actions of their special forces, but their use does not exempt states from the relevant rules of international law.

108  Kirkpatrick, the US representative to the UN, said that ‘unilateral compliance with the Charter’s principles of non-intervention and non-use of force may make sense in some instances but is hardly in itself a sound basis for either US policy or for international peace and security’, ‘Law and Reciprocity’, 1986 Proceedings of the ASIL 59.

109  As Franck graphically illustrates in Franck and Weisband, Word Politics (1972).

110  Gray, ‘The Limits of Force’, 376 Hague Recueil des Cours (2016) 101.