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Max Planck Encyclopedia of Public International Law [MPEPIL]

Intervention, Prohibition of

Florian Kriener

Content type:
Encyclopedia entries
Product:
Max Planck Encyclopedias of International Law [MPIL]

Module:
Max Planck Encyclopedia of Public International Law [MPEPIL]
Article last updated:
August 2023

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2023. All Rights Reserved.date: 03 October 2024

Subject(s):
Countermeasures — Economic sanctions — Sovereignty — Wrongful acts — States, equality — Recognition — States, independence — International peace and security

Published under the auspices of the Max Planck Institute for Comparative Public Law and International Law under the direction of Professor Anne Peters (2021–) and Professor Rüdiger Wolfrum (2004–2020). 

Editor’s Note: A different entry under the title ‘Intervention, Prohibition of’, written in April 2008 by Prof Dr Philip Kunig, appeared as part of the online Max Planck Encyclopedia of Public International Law until the publication of this entry in 2024. This new entry has been published at the same web address (URL) as the original entry. The original entry was also published in the 2012 print edition of the Encyclopedia (R Wolfrum (ed) The Max Planck Encyclopedia of Public International Law (OUP Oxford 2012) vol VI, 289–99).

A.  Introduction

1  The prohibition of intervention is a rule of customary international law that proscribes a State from coercively influencing the domaine réservé of another State. It thereby protects the principle of sovereign equality and delineates the sovereign spheres of States from each other (States, Sovereign Equality).

2  The International Court of Justice (ICJ) frequently highlights the prohibition of intervention as one ‘of the most fundamental principles and rules of international law’ (inter alia Armed Activities on the Territory of the Congo [Democratic Republic of the Congo v Uganda] [Reparations] [2022] para. 65 [‘Armed Activities’]; Armed Activities on the Territory of the Congo Cases). The rule is firmly embedded in customary international law (Military and Paramilitary Activities in and against Nicaragua [Nicaragua v United States of America] [Merits] [1986] para. 202 ff; Military and Paramilitary Activities in and against Nicaragua Case [Nicaragua v United States of America]; [‘Nicaragua Case’]) and has treaty-character in the founding documents of many international and regional organizations (eg Art. 4 (g) Constitutive Act of the African Union [2000]; Art. 2 (b) Charter of the Organization of American States [1948]; Art. 2 Charter of the Shanghai Cooperation Organization [2002]).

3  Despite its firm roots in customary and treaty law, the content and application of the prohibition of intervention belong to the most contested subjects in contemporary international law. This is due to the manifold connections between the prohibition of intervention and other principles and rules of international law, as well as the largely divergent State practice on this matter (see eg Hofer [2017] 175). According to the ICJ’s Nicaragua Case ([Merits] paras 205 ff), a State intervenes if it exercises coercive influence on the domaine réservé of another State and is not justified in doing so. All three criteria listed by the ICJ (domaine réservé, coercive influence, and justification) are heavily contested and will be dealt with in turn.

B.  Domaine réservé

4  Whether a matter pertains to the domaine réservé of a State essentially amounts to the question, whether a State’s sovereignty extends to this matter. In this line, the ICJ held in its Nicaragua judgment:

A prohibited intervention must accordingly be one bearing on matters in which each State is permitted, by the principle of State sovereignty, to decide freely (para. 205).

5  However, the concept of sovereignty is itself subject to frequent controversies and differing interpretations (Besson [2012] para. 3). Therefore, international adjudication and scholarship have developed two methods to determine the scope of a State’s domaine réservé.

(1)  Ex negativo

6  First, a State’s domaine réservé can be determined through the analysis of a State’s international obligations. All State matters unregulated by international law will accordingly pertain to a State’s reserved domain. This view was most prominently advanced by the Permanent Court of International Justice (PCIJ) in its 1923 Advisory Opinion on Nationality Decrees Issued in Tunis and Morocco (French Zone) (1923) (Nationality Cases before International Courts and Tribunals).

7  The Council of the League of Nations (League of Nations) requested the Advisory Opinion in response to a dispute between the United Kingdom (‘UK’) and France. The UK took issue with Nationality Decrees issued by France in 1921 that affected its citizens living in Tunis and Morocco. France however held the opinion that the Council of the League of Nations could not engage with this dispute because questions of nationality lay outside of its jurisdiction according to Art. 15 (8) Covenant of the League of Nations (1919). Article 15 (8) of the Covenant prohibited the Council from engaging with questions that are ‘solely within the domestic jurisdiction’ of a Member State. The PCIJ therefore had to decide whether issues of nationality solely pertained to the domestic jurisdiction of a State.

8  The PCIJ chose an ex negativo method to determine whether issues of nationality pertain to the domestic jurisdiction of a State:

The words ‘solely within the domestic jurisdiction’ seem rather to contemplate certain matters which, though they may very closely concern the interests of more than one State, are not, in principle, regulated by international law. As regards such matters, each State is sole judge (at 23–24).

Based thereon it held:

The question whether a certain matter is or is not solely within the jurisdiction of a State is an essentially relative question; it depends upon the development of international relations. Thus, in the present state of international law, questions of nationality are, in the opinion of the Court, in principle within this reserved domain (at 24).

9  As international law at the time did not in principle regulate questions of nationality, this matter was generally domestic. However, in the case at hand, France had only received the right to regulate questions of nationality through protectorate treaties with Morocco and Tunis (Protectorates and Protected States). Therefore, France derived its authority to regulate matters of nationality from an international law treaty. Accordingly, the PCIJ held that the dispute was not solely domestic because international law regulated a significant aspect of the dispute.

10  Since the PCIJ’s Advisory Opinion, the ex negativo approach has dominated scholarly considerations of this question. However, the progressive development of international law after the World War II and, in particular, the adoption of human rights treaties, have heavily reduced the matters that are completely unregulated by international law (Human Rights; History of International Law, Since World War II). Some scholars (eg Nasu [2013] 28) have asserted that one can find an international law provision on (almost) any matter in the 21st century. Drawing on the PCIJ’s wording, almost all matters could be considered ‘in principle, regulated by international law’ in contemporary international law. If any international legal regulation would suffice to detach a subject matter from a State’s domaine réservé, the domaine réservé as well as the prohibition of intervention would cease to exist. Accordingly, all interventions—except uses of force—would be permissible.

11  Numerous scholarly investigations (Jamnejad and Wood [2009]; Helal [2019]; Nowak [2018]; Hofer [2017]; Athen [2017]) alongside the ICJ’s more recent jurisprudence (Armed Activities [Merits] para. 163 ff; Armed Activities [Reparations] para. 65) have however confirmed that the prohibition of intervention continues to exist in the 21st century. It is frequently invoked by States and guides their foreign policy decisions (Kriener [2024]). Therefore, not every international legal regulation of a subject matter will result in its detachment from the domaine réservé of a State. This will only be the case, if an international legal rule crosses a threshold of density that substantively shifts a subject matter from the domestic to the international plane.

12  This is generally accepted when a rule of international law contains regulations on its enforcement. When States agree on enforcement mechanisms for substantive rules they accept that other States will exercise the enforcement mechanisms, even if this touches upon domestic matters. Under these circumstances, the subject matter is thoroughly regulated by international law and therefore ceases to pertain to the domaine réservé of a State. Furthermore, the required density can be assumed if a legal regulation is very thorough and specific, frequently reinforced by the international community, and clear in its application. The prohibition of apartheid serves as an example. Multiple States individually sanctioned South Africa in the 1980s, going beyond the sanctions ordered by the United Nations Security Council (‘UNSC’) (see UNSC Res 418 [1977]; United Nations, Security Council). These States argued that they were enforcing the prohibition of apartheid, which had been established through a multilateral treaty (International Convention on the Suppression of the Crime of Apartheid [1973]), was the subject of multiple United Nations General Assembly (‘UNGA’) resolutions, and applied to South Africa by the UNGA and UNSC (United Nations, General Assembly). However, none of these provisions contained regulations for the unilateral enforcement of the prohibition of apartheid. Nonetheless, the sanctions were generally accepted as lawful because the apartheid system in South Africa was not considered an internal affair and therefore a permissible subject to foreign intervention. The detachment of this subject matter from South Africa’s domaine réservé was a result of the apartheid prohibition’s high density, which consisted of multilateral treaties, UNGA and UNSC resolutions, frequent condemnations through the international community, and an unambiguous violation by South Africa. Only a minority of international legal rules will reach this high threshold. Soft law certainly does not have this effect (Athen [2017] 97).

13  Therefore, a high threshold is required for a subject matter to be detached from a State’s domaine réservé. In particular, not every provision in a human rights treaty will result in the detachment of the regulated issue from a State’s domaine réservé. A careful assessment of all international legal regulations between two States is required to assert whether a subject matter pertains to the domaine réservé vis-à-vis the concerned State.

(2)  Ex positivo

14  The ICJ has rather chosen an ex positivo approach to determine a State’s domaine réservé. After asserting that an intervention must bear on ‘matters in which each State is permitted, by the principle of State sovereignty, to decide freely’ (Nicaragua Case para. 205) the Court turned to the UNGA’s Friendly Relations Declaration (1970) (UNGA Res 2625 [XXV]), which it considered a reflection of customary international law on this issue. Drawing thereon it held that: ‘One of these [matters] is the choice of a political, economic, social and cultural system, and the formulation of foreign policy’ (para. 205). The Friendly Relations Declaration asserted that the free choice of a political, social, and cultural system derives from the principle of sovereign equality enshrined in Art. 2 (1) Charter of the United Nations (Principle of Friendly Relations Declaration) (United Nations Charter; [‘UN Charter’]). Therefore, these subject matters pertain to a State’s domaine réservé. Accordingly, this approach deduces elements pertaining to the domaine réservé from the principle of sovereign equality.

15  The ICJ did not thoroughly engage with this approach, but rather relied on the two fundamental UNGA resolutions, namely the aforementioned Friendly Relations Declaration and the 1965 Declaration on the Inadmissibility of Intervention in the Domestic Affairs of States (UNGA Res 2131 [XX]) to determine Nicaragua’s domaine réservé (Nicaragua Case paras 202–5). However, drawing on UNGA resolutions to determine States’ domaine réservé has its limitations. The foregoing resolutions list only a few examples of matters pertaining to a State’s domaine réservé. Moreover, they are phrased in very abstract terms and are therefore open to significant controversies. Further attempts to specify the subject matters pertaining to the domaine réservé have failed to attract universal support in the UNGA (most prominently UNGA Res 36/103 ‘Declaration on the Inadmissibility of Intervention and Interference in the Internal Affairs of States’ [1981], which was rejected by the States of the Western Europe and Others Group).

16  Moreover, the ever-changing content of the principle of sovereign equality and the relative character of a State’s domaine réservé limit the ex positivo approach. The principle of sovereign equality has undergone a multitude of changes since its popularization in 17th-century Europe (Peters [2009] 513 ff; Koskenniemi [2005] 266). Moreover, a State’s domaine réservé is relative in relation to different States. This is due to the differing intensity of bilateral relations. For example, Member States of the European Union (‘EU’) have regulated vast aspects of their internal democratic, judicial and macroeconomic affairs through European Law (European Union Law and International Law). With regard to other EU States, these matters are not wholly reserved from scrutiny (von Bogdandy [2022] 276). This is different in the relationship between EU States and Non-Member States that have not opened up their internal systems in a comparable fashion. Vis-à-vis those third States, the domaine réservé of EU States extends further. This relativity limits the ex positivo approach.

17  Nonetheless, some scholars have recently attempted to coin the term of inherently sovereign functions. In their perception, every State exercises a set of functions, which in turn define it as a State. Most prominently, the Tallinn Manual on the International Law Applicable to Cyber Operations 2.0 argues that ‘delivery of social services, the conduct of elections, the collection of taxes, the effective conduct of diplomacy, and the performance of key national defence activities’ (Schmitt Tallinn Manual 2.0 [2017] Rule 4 para. 16) pertain to this category. However, other scholars have pointed out that from a historical perspective there are no functions that have not been exercised by private institutions (Mégret [2021] 458). Constructing a generalizable compilation of subject matters that are derived from the principle of sovereign equality and form part of every State’s domaine réservé will therefore be very difficult.

18  Each of the approaches present in international case law and scholarship are flawed and lack universal support. This displays the contested nature of the domaine réservé concept, which is reinforced by its limited treatment in international jurisprudence.

C.  Coercion

19  An interference with a State’s domaine réservé must be coercive in order to violate the prohibition of intervention. In the words of the ICJ ‘coercion, … defines, and indeed forms the very essence of, prohibited intervention’ (Nicaragua Case para. 205). Coercion is a normative criterion that serves the ultimate purpose of the prohibition of intervention: the delineation of sovereign spheres. In an interconnected world, influence on other States is a common and necessary practice. The element of coercion draws the line between permitted forms of influence and influence that subjugates the sovereign will of another State. Thereby, the prohibition of intervention enables the coexistence of different States with diverse social, economic, and political systems (cf Nicaragua Case para. 264).

20  A frequently cited definition of coercion can be found in the UNGA’s Friendly Relations Declaration (Principle c):

No State may use or encourage the use of economic, political or any other type of measures to coerce another State in order to obtain from it the subordination of the exercise of its sovereign rights and to secure from it advantages of any kind.

The core question is therefore what measures will result in the subjugation of another State’s will. Oppenheim famously held that ‘dictatorial interference’ was necessary (Oppenheim [1905] 181). Jamnejad and Wood recognize coercion when the target State cannot reasonably resist the pressure of another State (Jamnejad and Wood [2009] 348). Hofer demands ‘irresistible pressure’ (Hofer [2017] 181). Despite being rather vague themselves, these formulations exemplify that pressure will only exceptionally cross the threshold of coercion.

21  Based on the Friendly Relations Declaration’s wording, coercive pressure can take a multitude of forms, including economic and political pressure. To what extent this holds true is however contested. The following sections will address individual forms of influence and map the debate whether these are coercive or not. The ICJ held that the use of force (1) and the support of armed insurgents (2) constitute coercion. Below this threshold, there is no consensus in the international community (3). Nonetheless, coercion must not be supplanted by a lower threshold (4) or reference to a State’s intentions (5).

(1)  Use of Force

22  The prohibition of the use of force in international relations is a specific application of the prohibition of intervention (Use of Force, Prohibition of). It prohibits the use of military force in or against the territory, the territorial sea, and the airspace of another State and is enshrined in Art. 2 (4) UN Charter. The decision to use force on its own territory is widely accepted as a fundamental aspect of a State’s domaine réservé. By using force without the State’s permission, the attacking State effectively subjugates the other State’s will on this matter. Therefore, an illegal use of force also violates the prohibition of intervention.

23  This was confirmed by the ICJ in the Corfu Channel, Nicaragua, and Armed Activities cases. In the Corfu Channel Case, minesweeping operations conducted by the UK in Albania’s territorial waters were considered a prohibited intervention. The Court thoroughly denied a ‘right of intervention’ stating that this would constitute a ‘manifestation of a policy of force, such as has, in the past, given rise to most serious abuses and such as cannot, whatever be the present defects in international organization, find a place in international law’ (at 35). In the Nicaragua decision, the ICJ differentiated between the different supportive acts given by the United States (‘US’) government to the Nicaraguan Democratic Forces (also known as contras). It held that mine laying in Nicaraguan territorial waters and attacks on ports, oil installations, and a naval base by US armed forces violated the prohibition of the use of force ([Merits] para. 227). Furthermore, the training and arming of the contras, which were engaged in hostilities with the Nicaraguan government at the time, qualified as an illegal use of force (ibid para. 228). The other support given to the contras, including financial and logistical support, were only considered a prohibited intervention and not an illegal use of force. The Court confirmed this jurisprudence in the Armed Activities case. The deployment and fighting of Ugandan military forces on the territory of the Democratic Republic of the Congo qualified as a violation of the prohibition of the use of force (Armed Activities [Merits] para. 153). Likewise, Uganda’s arming and training of the Mouvement de Liberation du Congo, which engaged in the Congolese Civil War, constituted a prohibited use of force (ibid paras 160, 164). Both in the Nicaragua Case (para. 228) and Armed Activities (para. 164) judgments, the ICJ affirmed that violations of the prohibition of the use of force violate the prohibition of intervention, thus confirming that the former is a specific application to the latter. Accordingly, all prohibited uses of force violate the prohibition of intervention.

(2)  Support of Armed Insurgents

24  Support to armed insurgents constitutes the second established form of prohibited intervention. In this regard, the Friendly Relations Declaration reads:

Also, no State shall organize, assist, foment, finance, incite or tolerate subversive, terrorist or armed activities directed towards the violent overthrow of the régime of another State, or interfere in civil strife in another State (Principle c).

25  Drawing upon this paragraph, the ICJ qualified US support to the Nicaraguan contras as an intervention (Nicaragua Case paras 192, 205, and 242). The support encompassed financial support, training, supply of weapons, intelligence and logistic support directed at the military overthrow of the incumbent government. As pointed out above, weapons supply and training additionally violated the prohibition of the use of force.

26  This form of intervention only applies to the support of armed insurgents. Only armed insurgents will pursue a ‘violent overthrow of the régime’ as required by the Friendly Relations Declaration. This follows from its wording and preparatory works. During the years of negotiations leading up to the Friendly Relations Declaration, States could only agree on a very limited number of constellations they all considered as prohibited intervention (Pomson [2022] 193 ff). Accordingly, the notion of a violent regime overthrow was associated with military actions, such as a coup d’état by military forces (see Kriener [2024]).

(3)  Coercion by Other Means

27  In line with the wording of the Friendly Relations Declaration (see para. 20 above), a whole range of further measures can theoretically be coercive (Nicaragua Case para. 192). Recent investigations have however pointed out that during the negotiations leading up to the Friendly Relations Declaration no consensus could be reached concerning other forms of coercion besides the use of force and support to armed insurgents (Pomson [2022] 193 ff). These two forms are the only ones explicitly spelled out in the Declaration. The general definition of prohibited intervention in the Declaration, which includes political and economic measures as possible forms of coercion, thus exceeds the consensus among States during the negotiations. Moreover, there has not been a reconciliation or clarification in subsequent State practice with regard to the gap between the Declaration’s wording and the actual consensus. All other possible forms of coercion are essentially contested. The following sections will outline this ongoing dispute with regard to individual forms of pressure.

(a)  Sanctions

28  The term sanction is not a term of art in international law, but rather describes foreign policy actions by States. They can principally be divided into UNSC sanctions, multilateral sanctions, and unilateral sanctions. Whereas the legality of unilateral sanctions is highly contested, UNSC and multilateral sanctions are widely accepted as legal. Article 41 UN Charter authorizes the UNSC to decide upon economic measures in the face of a threat or breach of the peace (Peace, Threat to the; Peace, Breach of the). Their application against Member and NonMember States is widely accepted as lawful. A multilateral sanction is a method of pressure taken by an international organization within its mandate against one of its Member States. For example, the African Union’s Peace and Security Council can levy sanctions on a Member State when there is an unconstitutional change in government in the Member State (Art. 25 (7) African Charter on Democracy, Elections and Governance [2007]; Art. 7 (g) Protocol relating to the Establishment of the Peace and Security Council [2002]) (African Union [AU]). These sanctions rely on the prior consent of a State when it becomes a member of the organization.

29  In turn, unilateral sanctions are measures by a State or an international organization directed against a third State and intended to disadvantage the third State in order to induce a change in its behaviour. These can take a wide array of forms including full-scale embargoes, export restrictions for individual sectors or products, and measures directed against individual government members. In contrast to multilateral sanctions, these unilateral measures cannot rely on the prior consent of the targeted State.

30  In the Nicaragua Case, the ICJ found that a cessation of economic aid to Nicaragua, the 90% reduction of a sugar export quota, and a full-scale trade embargo did not amount to coercion (paras 244–45). These measures are credited with a significant decline in Nicaragua’s Gross Domestic Product and a major influence on the Sandinista government’s electoral defeat in 1990 (Pomson [2022] 207). Nonetheless, the ICJ held that these measures did not cross the coercion threshold. In its limited jurisprudence on this matter, the ICJ has thus been very reluctant to consider sanctions a violation of the prohibition of intervention.

31  State practice has been divided since the 1986 judgment. On the one hand, many States have employed sanctions as a foreign policy tool (Dawidowicz [2017]; Bogdanova [2022]) and argued that these are compatible with international law. Particularly, the EU employs sanctions as a central aspect of its common foreign and security policy (Council of the EU ‘Basic Principles on the Use of Restrictive Measures [Sanctions]’ [2004]; European Common Foreign and Security Policy). They argue that the regulation of market access and exports is itself a sovereign matter. As no right to trade exists under international law (Nicaragua Case para. 276; Lowe and Tzanakopoulos [2013] para. 37; Economic Warfare), restricting market access or exports does not violate international law. Furthermore, States that have traditionally been sceptical of unilateral sanctions, such as China, have recently also used sanctions as a foreign policy instrument.

32  On the other hand, the UNGA has labelled US sanctions against Cuba as a violation of international law every year since 1992 (eg UNGA Res 74/7 ‘Necessity of Ending the Economic, Commercial and Financial Embargo Imposed by the United States of America against Cuba’ [2019]). The most recent of these resolutions of 2022 (UNGA Res 77/7) received 185 votes in favour and two against, with two abstentions. All EU States voted in favour of the resolution. Moreover, the UNGA passed multiple resolutions between 1989 and 2011 criticizing ‘unilateral coercive economic measures’ (eg UNGA Res 58/198 ‘Unilateral Economic Measures as a Means of Political and Economic Coercion against Developing Countries’ [2003], adopted with 125 in favour, one against and 37 abstentions). This phrasing is—to some extent—redundant. ‘Coercive’ measures are illegal under international law, as the ICJ confirmed. The UNGA resolutions therefore only restate the lex lata and do not modify or extend this rule. However, the resolutions recognize that unilateral economic measures can amount to coercion, which is in itself noteworthy.

33  The UNGA’s practice therefore strongly indicates that unilateral economic measures can surpass the coercion threshold. While the UNGA’s resolutions are not binding, they can be considered as an expression of a consensus among States, particularly due to the significant amount of support the resolutions on sanctions against Cuba have gathered, alongside their frequency and consistency. However, this consensus only extends to very significant sanction regimes. The UNGA has solely identified the US embargo against Cuba as a violation of international law. This embargo is very comprehensive and includes regulations that inhibit third States from entering in economic relations with Cuba.

34  Yet, the UN Human Rights Council’s Special Rapporteur on unilateral coercive measures has argued, alongside other States and authors, that any unilateral economic measure will violate international law (eg UNSC ‘Letter Dated 25 March 2020 from the Representatives of Angola, Cambodia, China, Cuba, the Democratic People’s Republic of Korea, Dominica, Grenada, the Islamic Republic of Iran, Myanmar, Nicaragua, the Russian Federation, Saint Vincent and the Grenadines, Sri Lanka, the Sudan, Suriname, the Syrian Arab Republic, the Bolivarian Republic of Venezuela and Zimbabwe to the United Nations Addressed to the Secretary-General and the President of the Security Council’) (Special Rapporteurs of Human Rights Bodies; United Nations Commission on Human Rights/United Nations Human Rights Council). This view stands in contrast with the view held by EU Member States, the majority of accession candidates to the EU, Canada, the US, Australia, and the UK, who generally consider sanctions as a permissive foreign policy tool. Due to these opposing views, some authors argue that the legality of unilateral sanctions falls into a grey area of international law (Hofer [2017] 179).

35  In summary, unilateral sanctions can amount to coercion. However, there is no consensus in the international community on when they reach this threshold. In line with the general restrictive interpretation of the coercion criterion, this will only hold true for the most severe sanction regimes.

(b)  Propaganda, Disinformation, and Electoral Disruption

36  Some voices consider different forms of influence on a State’s political system coercive. From the 1920s to 1960s, a significant number of scholars argued in favour of a prohibition of peacetime propaganda (see Larson [1966] 445 f with further references). In their view, propaganda subjugates the free choice of a political system to the will of another State. However, multiple attempts to establish a prohibition of propaganda in international law failed. The 1936 International Convention on the Use of Broadcasting in the Cause of Peace only attracted a few States and was not ratified by the States most engaged in propaganda activities at the time, ie Germany, the Soviet Union, Japan, and Italy. The convention has no significant impact despite continuing in force today (Baade [2018] 1366). This also holds true for all other attempts to anchor a prohibition of propaganda in international law. Since the 1960s, scholarship on this matter saw a sharp decline.

37  However, more recent State sponsored disinformation campaigns have spurred debates on this issue. In particular, the Russian campaign to distort the results of the 2016 US Presidential election raised many eyebrows. Some argued that targeted attempts to distort the electoral result in favour of one candidate through damaging leaks, social media campaigns, and engineered voter suppression constitutes coercion (Schmitt [2021] 747; cf Wheatley [2020] 192; Moynihan [2019] para. 131; Terry [2018] 625; Helal [2019] 114). Others held that the measures did not cross the coercion threshold (Ohlin [2020]; Ferro [2020]; Fidler [2017]), or that the law was unclear (Sander [2019]). However, no State, not even the US, qualified the Russian campaign as coercive.

38  Notably though, a consensus in scholarship and State practice is emerging, which considers tampering with electoral infrastructure a coercive interference (Schmitt [2021]; Pomson [2022]; Wheatley [2020]; Moynihan [2019] para. 126; Keitner [2021]). Examples include cyber-attacks on vote counting machines that result in a miscount. If the results of an election are directly manipulated, a State is thwarted from freely determining its political government and accordingly its political system. Thus, the interference is coercive. Recent statements on international law applicable in cyberspace reinforce this conclusion (eg Australia, Costa Rica, Finland, Germany, Israel, UK, USA).

(c)  Recognition of Non-Effective Governments

39  Likewise, the recent surge in recognition and derecognition of governments has revived debates about the coercive nature of declarations of recognition. A declaration of recognition or derecognition is a public statement by a State official asserting which entity within another State the former considers or does not consider as the government of the latter. Many voices consider such declarations in violation of international law. The Mexican Foreign Secretary Genaro Estrada stated in 1930 that the determination of a government was an internal affair which did not allow for foreign judgments thereon (the so-called Estrada Doctrine, see Recognition; see also Non-Recognition). Along these lines, the 1923 Award in the Tinoco Concessions Arbitration argued that an effective government could enter valid contractual commitments on behalf of the State, even if it assumed power through a military coup d’état (Aguilar-Amory and Royal Bank of Canada Claims [Great Britain v Costa Rica]). Thereby, the so-called Tobar Doctrine of 1907, which only allowed for the recognition of constitutional governments, was rejected. Effectiveness was from then on considered as the principal determinant of a government’s recognition (Talmon [1998]). Recognition of any entity other than the effective government violated this principle and therefore qualified as a coercive influence on the determination of a State’s government (Aust [2020] 84; Helal [2019] 119). Authors however differentiate between de iure and political recognition declarations. A de iure recognition is considered coercive because of its significant impact, ie representation in international organizations, access to foreign currency reserves, and diplomatic representation in other States. A political recognition that does not carry these consequences is in turn not considered as coercive (Talmon [2013] 248).

40  The effectiveness principle has however been under pressure. Instead of relying solely on the effectiveness of a government, many States have recently drawn upon the legitimacy of government in their recognition decisions (Hadi government in Yemen 2014; Libyan Transitional Government 2011; Barrow government in Gambia 2017; Guaidó government in Venezuela 2019) and refused recognition to effective, but illegitimate governments (Maduro government in Venezuela 2019; Transitional Military Council in Sudan 2019; Lukashenka government in Belarus 2020; Military junta in Myanmar 2021; Military governments in Mali 2020, 2021; Military government in Niger 2023). This evolving practice is based on the democratic principle in international law. For example, the AU only recognizes constitutionally and democratically established governments. It therefore suspended Member States in which an unconstitutional change of government occurred and thereby derecognized their illegitimate governments. Likewise, the Organization of American States (OAS) suspended Honduras after a coup d’état in 2009 and recognized the Guaidó government in Venezuela in 2019.

41  This turn to legitimacy likewise puts the coerciveness of a recognition declaration into question. The multiple recognition and derecognition declarations of recent years have not been met with universal condemnation. In all mentioned cases, some States qualified the declarations as coercive interventions (see eg Tladi [2020]). However, a majority of States remained silent on this issue and the States issuing said declarations detailed, at length, why their acts conformed to international law (see eg Kriener [2020]). Moreover, the UK skirted away from its longstanding policy of only recognizing States, not governments, a policy that it had established in 1980. Then, many authors considered it as the final confirmation of the effectiveness principle (Frowein [2012] para. 14). However, the UK recently did recognize the Guaidó government in Venezuela in 2019 despite not being effective. Therefore, it is doubtful whether the recognition of a non-effective government or the derecognition of an effective government is still considered coercive by the international community. Due to the customary nature of the prohibition of intervention, the coercion threshold is determined by the practice and opinio iuris of States. Accordingly, the recent shift away from the effectiveness criterion could likewise alter the coerciveness of a recognition declaration.

(d)  Support to Peaceful Opposition Groups

42  Whereas the prohibition of intervention proscribes support for armed insurgents in a different State, it is disputed whether this also applies to support given to peaceful opposition groups. In 2009, Honduras submitted a dispute with Brazil to the ICJ over Brazilian support given to a protest movement led by former president Manuel Zelaya (Certain Questions concerning Diplomatic Relations [Honduras v Brazil] [Application Instituting Proceedings]). Zelaya was ousted by a military coup in 2009 and sent to exile. After crossing the Nicaraguan-Honduran border irregularly, he took up residence in the Brazilian embassy in Tegucigalpa. From there he addressed his supporters, met with opposition leaders and coordinated the protests in favour of his reinstatement as president. Honduras characterized this support by Brazil as a coercive intervention. However, Honduras withdrew the case after a political settlement of the dispute (Peaceful Settlement of International Disputes).

43  Scholarship is divided on the question. Some argue that funding political opposition groups violates the prohibition of intervention (Helal [2019] 118). If a State prohibits foreign funding to political parties through its national laws, such funding will usually contravene the prohibition of intervention (Jamnejad and Wood [2009] 368). Others point to the long-standing practice on this issue that is exercised by a wide variety of States (Reisman [2019]). Moreover, some qualify support to oppositional groups as support for the principle of democracy in international law and/or international human rights law (Damrosch [1989] 44). Another group of scholars argues that the law is unclear on this question (Krieger [2019] 991 f) and that it falls into a legal grey area (Kriener [2024]).

44  Most States prohibit political parties from receiving direct or indirect financial assistance from foreign States (International Institute for Democracy and Electoral Assistance [2012]). The European Court of Human Rights (ECtHR) confirmed in a 2007 judgment that such prohibition is in conformity with the right to freedom of association under the European Convention on Human Rights (Parti Nationaliste Basque v France [2007]; European Convention for the Protection of Human Rights and Fundamental Freedoms [1950]; Association, Freedom of, International Protection). However, in a more recent judgment the ECtHR held that a blanket ban on foreign assistance to non-governmental organizations (‘NGOs’) constitutes a violation of those organizations’ freedom of association (Ecodefence and Others v Russia [2022]). This also holds true for organizations that are engaged in oppositional work or support issues contrary to governmental policy.

45  This exemplifies the close connection between the prohibition of intervention and other rules of international law. If another rule of international law permits a form of influence, eg support to NGOs in a foreign State, this form of influence will not violate the prohibition of intervention. Critical comments on the human rights situation in another State do not violate the prohibition of intervention.

(4)  Interference Instead of Coercion

46  The foregoing sections have exemplified the disputed nature of coercion. It is determined by reference to other rules of international law and through States’ practice and opinio iuris on certain forms of influence. Due to the diversity of interState relations and the heightened political tensions on matters of foreign interference (see Krieger [2019] 991), universal consensus on the coercion threshold is rare. The lex lata of the prohibition of intervention only proscribes a few forms of influence. Therefore, some States and scholars advocate for a more extensive understanding of the prohibition of intervention. They argue that international law not only prohibits interventions, but also interferences. An interference is a measure of influence upon the domaine réservé of a State taken without the targeted State’s consent.

47  Most prominently, the already mentioned UNGA Res 36/103 of 1981 asserts that both interference and intervention are illegal. The resolution stipulates a prohibition of all forms of influence on the internal affairs of another State without that State’s consent (see Annex, II (o)). This essentially disposes with the coercion criterion. The resolution was adopted by 102 votes (mostly from States of the Warsaw Pact [Warsaw Treaty Organization] and the Non-Aligned Movement [NAM]), but rejected by 22 States from the Western Europe and Others Group. The ICJ did not reference this resolution in its 1986 Nicaragua judgment (or in any later judgment). To the contrary, the ICJ held that coercion was the ‘very essence’ of prohibited intervention (Nicaragua Case para. 205). It did not mention a prohibition of interference. The 1981 resolution is credited with ‘little normative value’ (Hofer [2017] 185) and does not reflect customary international law (Kunig [2012] para. 20). International law does not prohibit measures of influence if they are not coercive.

(5)  Intention and Intervention

48  Some authors additionally believe that the measures of influence detailed in Section C.3 will violate the prohibition of intervention if they are employed with the end of achieving regime change (Tladi [2020] 99; Jamnejad and Wood [2009] 368; Janik [2015] 119). They argue that the pursuit of regime change is illegal under international law, whereby influence measures employed with this intention violate the prohibition of intervention. However, this argument stands in contrast to the ICJ’s jurisprudence. In Armed Activities, it was held that it was of no importance whether Uganda had pursued regime change in the Democratic Republic of the Congo ([Merits] para. 163). Likewise, the ICJ did not review the US’s intentions behind the sanctions against Nicaragua (Nicaragua Case paras 241 and 244). These had been taken with an intention to change the government in Nicaragua, which representatives for Nicaragua had claimed during the oral proceedings. Nonetheless, the Court did not consider the sanctions as a violation of the prohibition of intervention. Therefore, the intentions behind a form of influence do not affect their legality (Athen [2017] 248; Saluzzo [2021] 34–35).

(6)  Summary

49  The coercion criterion can be difficult to apply. If a measure of influence is forceful or supports armed insurgents, it is certainly coercive. Moreover, there is an emerging consensus that tampering with election results amounts to coercion. Apart from these established forms, no other form of influence can clearly and universally be considered as coercive or not. Rather, a case-by-case assessment is required to establish whether the pressure exerted by one State on another State crosses the coercion threshold. The pressured State must not comply with the requested change in behaviour. Rather, the measure of influence must put the pressured State into a position in which the exercise of its sovereign will is limited so severely that it is effectively subjugated. This assessment relies on States’ practice and their opinio iuris due to the customary nature of the prohibition of intervention.

50  In this case-by-case assessment, the relative nature of the prohibition of intervention must be observed. The extent of a State’s domaine réservé depends on the individual relationship between two States and their mutual obligations under international law. Likewise, the coercion criterion is relative. A more powerful State can exert pressure more easily on a less powerful State than vice versa. Accordingly, the same measure taken by a powerful State can create unbearable pressure on another State, even if the measure would only have limited effect if taken by the latter against the former. Assessing the coerciveness of a measure or measures of influence thus requires a careful assessment of all relevant legal and factual circumstances.

D.  Justification

51  If a measure of influence amounts to coercion, it can still be justified. If the coercion is forcible, the limited justifications for a use of force in international relations apply (1). For all other forms of coercion, the justifications under general international law are additionally applicable. Countermeasures are the most relevant and controversial (2).

(1)  Justifications for the Use of Force

52  A use of force in international relations can either be justified in self-defence, under Chapter VII UN Charter (Collective Security) or by invitation of the affected State (Intervention by Invitation). All of these justifications likewise apply for measures of influence that are coercive but do not reach the threshold of force. In particular, Art. 41 UN Charter authorizes the UNSC to take measures not amounting to force, including ‘complete or partial interruption of economic relations and of rail, sea, air, postal, telegraphic, radio, and other means of communication, and the severance of diplomatic relations’.

(2)  Countermeasures

53  Countermeasures are a necessary tool to maintain the decentralized international legal order. The ICJ confirmed its customary status for bilateral relationships inter alia in the Gabčíkovo-Nagymaros Case (Hungary/Slovakia) (para. 83). According to Art. 49 ff Articles on the Responsibility of States for Internationally Wrongful Acts (UNGA Res 56/83 [2001]; [‘ARSIWA’]), a State may breach its obligations under international law in response to a prior violation of international law by another State. These are limited to the non-performance of an international obligation, should be proportional, and, as far as possible, reversible.

54  Countermeasures are a central pillar for justifying unilateral sanctions (see Section C.3 above). States will frequently invoke prior violations of international law by another State when introducing or justifying sanctions. This argument, however, faces two central critiques.

55  A countermeasure only justifies the ‘non-performance’ of an obligation. This limitation could entail that countermeasures are only permissible with regard to an obligation contracted under international law. Accordingly, active interventions with the sovereignty of another State would not be permissible countermeasures. However, almost every violation of international law will implicate the sovereignty of another State, as international law essentially defines a State’s sovereign sphere. A distinction between the passive non-performance of an obligation contracted under international law and an active intervention is unfounded. Moreover, the International Law Commission’s commentaries to Art. 49 ARSIWA mention asset freezing as an example of non-performance (UN ILC ‘Draft Articles on Responsibility of States for Internationally Wrongful Acts, with Commentary’ [2001] Art. 49 para. 6; International Law Commission [ILC]). This exemplifies that countermeasures are not restricted to a passive non-performance.

56  A second critique turns against ‘third-party countermeasures’. The ICJ established the customary nature of countermeasures only for the bilateral context, ie if the violation of international law to which a State responds through the countermeasures directly affects that State. In this line, Art. 49 ARSIWA declares that an ‘injured State’ may take countermeasures. However, sanction regimes frequently address violations of international law that do not directly affect the sanctioning State. This is particularly true for sanctions following human rights violations. Whether such ‘third-party countermeasures’ are legal was left open by the 2001 ARSIWA. Article 54 ARSIWA states that the Articles do not affect a third State’s right to take lawful measures in response to a breach, which it may invoke under Art. 48 ARSIWA. These States are also referred to as ‘non-injured States’. The ILC listed some examples of countermeasures by non-injured States but arrived at the conclusion that not enough State practice existed to establish the customary nature of third-party countermeasures (Art. 54, Commentary para. 3). This assessment has received strong criticism (Dawidowicz [2017]; Bogdanova [2022]; Katselli Proukaki [2010]; Tams [2005] 200). Several studies have found that sanctions by third States in response to violations of fundamental norms have been a long-standing practice in international relations exercised by a wide array of States. Moreover, this practice has entrenched itself since 2001. Many States have regulated their sanction practices through national legislation that specifically allows for sanctions in response to violations of international law that do not immediately affect that State (EU, USA, Australia, Canada, UK). This is the logical consequence of a decentralized international legal order with imperfect multilateral enforcement mechanisms. States interested in upholding multilateral and universal rules need to take action against such violations, in order to maintain their binding force. Therefore, it can be assumed that third-party countermeasures can justify coercive interferences, if they are proportionate.

E.  Conclusion: Applying a Contested Rule

57  The prohibition of intervention is firmly established in customary international law. However, aside from a few forms of intervention, the application of this rule is heavily contested. States frequently argue on multiple levels whether a measure constitutes prohibited intervention. Particularly with a view to sanctions, some States argue that these do not cross the coercion threshold whereas others see their economic freedom coercively restricted through sanctions. Furthermore, some States believe that sanctions can be justified as (third-party) countermeasures whereas others completely reject unilateral sanctions and third-party enforcement.

58  These conflicts are here to stay. Therefore, some authors argue that non-military influence measures pertain to a grey area of the prohibition of intervention. They believe that such measures of influence cannot clearly be qualified as legal or illegal under the prohibition of intervention as long as recourse is made to the established means of determining and interpreting international law. Therefore, it may come down to international and national courts to decide whether a measure of influence qualifies as coercive intervention. To determine this question, the court or tribunal will have to consider all relevant legal and factual circumstances and assess whether the measure in question pressures a State to an irresistible degree.

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Cited Documents

Cited Cases