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Max Planck Encyclopedia of Public International Law [MPEPIL]

Armed Conflict, Effect on Treaties

Silja Vöneky

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2015. All Rights Reserved.date: 22 July 2019

Armed conflict, international — Peace treaties — Conduct of hostilities — Belligerence — Weapons

Published under the auspices of the Max Planck Foundation for International Peace and the Rule of Law under the direction of Rüdiger Wolfrum.

A.  Introduction

The question of the effect of an armed conflict on treaties was and is one of the most disputed subjects in public international law. Neither in State practice nor in legal doctrine, was there a common view on the question whether peacetime international law is applicable to belligerent States during an international armed conflict in general. In the 19th century there is some evidence for the opinio iuris that ‘[b]y the Law of Nations war abrogates all treaties between the belligerents’ (Hardings cited in McNair 700; cf Harvard Draft Convention Comment at 1184). On the other hand the Instructions for the Government of Armies of the United States in the Field (‘Lieber Code’), the first military manual of the United States, said that treaties which are concluded between the belligerents during a war as well as treaties which were concluded between the belligerents before a war, but with the intention to stay in force during the war, are not void because of a war (Art 11 Lieber Code). The drafter of the Code, Francis Lieber, argued that instead of the rule inter arma silent leges the rule fides etiam hosti servanda has to be applied because the aim of a just war is peace. Since confidence between the belligerents is considered the basis for the future peace, one would destroy the very object of war if no degree of confidence would remain between the belligerents (see Vöneky [2002] 458). Nearly 50 years after the Lieber Code, in 1910, the tribunal in the arbitration on the Question Relating to the North Atlantic Coast Fisheries stated: ‘International Law in its modern development recognizes that a great number of Treaty obligations are not annulled by war, but [are] at most suspended by it’ (for details see Vöneky [2001] 204 [state practice since 17th century], 213 [judgments of international courts and tribunals]).

The same development can be observed in regard to legal doctrine: traditionally legal doctrine holds that all treaties between belligerents terminated ipso facto at the outbreak of war (McNair 698). The rationale behind this view was that war is the absolute opposite of peace and involves a complete rupture of relations (see UN ILC UN Doc A/CN.4/552 at 4). Additionally, commentators often advanced the argument of lex specialis derogat legi generali (specific law overrules general laws) generally to deny the applicability of peacetime treaties between belligerent parties during an armed conflict: since the law of armed conflict is a specialized set of laws, to the extent that its provisions are contrary to those of peacetime treaties, the law of armed conflict prevails.

Today the majority view seems to approve the general applicability of peacetime law during war in regard to certain types of peacetime treaties (see paras 5–11). The topic is still disputed as neither the UN Charter nor other multilateral treaties include rules in regard to the effect of armed conflict on treaties. The Vienna Convention on the Law of Treaties (1969) (VCLT) only says that the Convention does not cover these questions (Art. 73: ‘The provisions of the present Convention shall not prejudge any question that may arise in regard to a treaty … from the outbreak of hostilities between States’). This was due to the fact that the conduct of hostilities was seen as wholly outside the scope of the general law of treaties to be codified in the articles of the VCLT by the drafters (Wetzel and Rauschning 480). Besides this there is no decisive judgment or advisory opinion of the International Court of Justice (ICJ) to the general question of the effects of armed conflicts on peacetime treaties (see United States Diplomatic and Consular Staff in Tehran [United States of America v Iran], dealing only with the Vienna Conventions on Diplomatic and Consular Relations, see below para 6; Legality of the Threat or Use of Nuclear Weapons [Advisory Opinion], dealing with the question of the protection of the environment during armed conflict without giving a clear answer in regard to the question of the applicability of peacetime environmental treaties during armed conflicts, see below para 10).

After World War II, expert bodies dealt with the problem of the effect of armed conflict on treaties. The first important resolution was drafted by the Institut de Droit international (IDI) in 1985 (see the resolution ‘The Effects of Armed Conflict on Treaties’). The International Law Commission (ILC) finally included this topic in its current programme of work in 2004 (UNGA Res 59/41 of 16 December 2004); a first report was drafted by special rapporteur Ian Brownlie in 2005 and in 2008 the ILC adopted, on first reading, a set of 18 draft articles on the effects of armed conflicts on treaties (‘ILC Draft Articles’). In 2010 Lucius Caflisch, the new special rapporteur, proposed a number of changes to the initial set of draft articles after these articles were commented by States. The most crucial topics of discussion have been inter alia the scope of the articles; effects of non-international armed conflicts; the indicia for identifying treaties which continue in operation; the types of treaties whose subject matter implies their survival in whole or in part; and the effects of international or civil war conditions involving a single State Party or several States Parties to treaties.

B.  General Applicability of Peacetime Treaties under General International Law

Today the traditional dichotomy between the international law of war on the one hand and the law of peace on the other hand is dissolving: the dominant view is that whether a treaty continues to be in force in wartime depends on the type of treaty in question, its object and purpose (Oppenheim and Lauterpacht 303). The ILC Draft Articles on Effects of Armed Conflicts on Treaties (see UN Doc A/65/10 289) state accordingly: ‘The outbreak of an armed conflict does not ipso facto terminate or suspend the operation of treaties as: (a) Between the State Parties to the treaty that are also parties to the conflict; (b) Between a State Party to the treaty that is also a party to the conflict and a State that is a third state in relation to the conflict’ (ibid 295). This approach can be based on sufficient State practice: even if the States’ practice seems to vary over time, for certain kinds of treaties and provisions rules have been established regarding their applicability between belligerent States. This seems particularly true for the following five categories of treaties: (1) treaties providing for continuance during war; (2) treaties that are compatible with the maintenance of war; (3) treaties creating an international regime or status; (4) treaties for the protection of human rights; (5) treaties relating to the protection of the environment; and for (6) ius cogens rules and obligations erga omnes (see also Art 5 Annexes (a), (b), (e), (f) ILC Draft Articles). The rationale behind the categories (1) to (5) is that, as the ILC Draft Articles state, the subject matter of those treaties involve the implication that they continue in operation, in whole or in part, during armed conflict, and hence the incidence of an armed conflict will not as such affect their operation (Art 5 ILC Draft Articles). However, it is argued that the treaties listed in the annex by the ILC do not all conform to the conditions cited in Art 5, as for instance so called ‘law-making treaties’ (see UN Doc A/CN.4/622 13, 15; UN Doc A/CN.4/627 para 52 et seq; Art 5 and Annex ILC Draft Articles).

1.  Treaties which Provide for Continuance during War

First of all, it is not disputed that treaties that expressly or according to their object and purpose provide for continuance during war cannot per se be suspended or terminated because of an armed conflict, and that, vice versa, treaties may be suspended or terminated during war when expressly provided in the treaty (see Art 7 ILC Draft Articles; Art 3 IDI Resolution). This is evident in regard to treaties relating to the law of armed conflict, including treaties relating to international humanitarian law (see Art 5 Annex (a) ILC Draft Articles). Yet many peacetime treaties fail to address this issue directly. Exceptions are, for example Art 27 Vienna Convention on Consular Relations (1963) (‘in the event of the severance of consular relations between two States: … the receiving State shall, even in case of armed conflict, respect and protect the consular premises’) and Art 45 Vienna Convention on Diplomatic Relations (1961) (concerning their application see in the affirmative the ICJ in United States Diplomatic and Consular Staff in Tehran). Another exception was Art XIX (1) of the 1954 International Convention for Prevention of Pollution of the Sea by Oil, which permitted State Parties ‘[i]n case of war or other hostilities … [to] suspend the operation of the whole or any part of the present Convention’. Besides this, international conventions establishing civil liability regimes exempt damage caused by measures and means of warfare (cf Sands 231). Nevertheless, the latter does not mean that the applicability of these conventions during armed conflicts is per se excluded, as their application is not limited to peacetime but to non-military conduct only.

2.  Treaties which are Compatible with the Maintenance of War

There is a strong, but sometimes disputed view that belligerents are not allowed to suspend or terminate peacetime multilateral treaties whose execution is compatible with the maintenance of war even without an explicit treaty provision (cf Berber 95; Chinkin 185; Klein 295; Tarasofsky 64; Simonds 195, 215; for a different view Stone 447; Art 5 (a) IDI Resolution). According to this, multilateral peacetime treaties whose application does not limit methods and means of warfare continue to apply during an international armed conflict even between belligerent States (see ICRC Guidelines Art 5; Vöneky [2001] 243, 249): eg a multilateral treaty entailing obligations to protect the marine environment during land warfare continues to apply during an international armed conflict between belligerent States. There seems to be sufficient State practice supporting this view (see Goss v Brocks Nebraska Supreme Court (1929) 223 NW 13; Techt v Hughes New York Court of Appeals (1920) 229 NY 222, cert denied (1920) 254 US 643; Brownell v San Francisco California Court of Appeals (1954) 26 Cal App 2d 102, 271 P 2d 974; cf Prescott 208, 214), and as there is no direct interference with the rules of the ius in bello, there do not seem to be convincing arguments that an application of such treaties could be denied.

3.  Treaties Declaring, Creating, or Regulating a Permanent Regime or Status

More problematic than the applicability of compatible peacetime treaties is the continued validity of treaties that impose additional and higher standards upon belligerents than the traditional laws of armed conflict. The first type of treaties that generally bind belligerent States, even though they can interfere with military interests, constitute the so-called ‘treaties creating an international regime or status’ (see Art 5 Annex (b) ILC Draft Articles). These treaties establish a territorial order in the general interest of the international community, such as treaties providing for the demilitarization or neutralization of zones or the internationalization of waterways (Klein 295 et seq; McNair 720; Vöneky [2001] 255 et seq, 268 et seq).

4.  Treaties for the Protection of Human Rights

Human rights treaties are another type of treaty commonly regarded as applicable during war, even though they impose additional restraints on the methods and means of warfare. This view was shared by the drafters of the resolution of the Institut de Droit International, which asserts: ‘The existence of an armed conflict does not entitle a party unilaterally to terminate or to suspend the operation of treaty provisions relating to the protection of the human person, unless the treaty otherwise provides’ (Art 4 IDI Resolution; see as well Art 5 Annex (e) ILC Draft Articles). This view was supported by the UN General Assembly (see eg UNGA Res 2677 (XXV) of 9 December 1970) and the ICJ (see Legality of the Threat or Use of Nuclear Weapons [Advisory Opinion] at para 25; against this view is the so-called separatist theory during the 1970s, cf Mushkat 161: the separatist theory argues that the law of armed conflict and international human rights are two different bodies of international law that have to be separated because of their antinomie irréductible, cf Meyrowitz 1095; Human Rights and Humanitarian Law).

5.  Treaties Relating to the Protection of the Environment

10  It is still disputed whether and to what extent treaties relating to the protection of the environment are applicable between belligerent States—apart from those which are compatible with the maintenance of war (see para 7). The ILC Draft Articles include in rather broad terms ‘treaties relating to the protection of the environment’ (Art 5 Annex (f) ILC Draft Articles, UN Doc A/65/10 at 298), arguing that the subject matter of these treaties involves the implication that they continue in operation (ibid Art 5). This seems convincing in regard to international agreements regulating the protection and use of areas beyond national jurisdiction—such as the high seas, the deep sea-bed, outer space, and Antarctica—as they share certain similarities with treaties establishing objective regimes (see para 8 above). Such treaties regulating the protection and use of areas beyond national jurisdiction seek to protect the environment or parts of it in the interest of the State Community as a whole. The same is true with regard to environmental treaties protecting common goods (such as the climate, the ozone layer, or biodiversity) and global environmental resources (see Vöneky [2001] 204 et seq, 210 et seq). Thus one can argue that environmental treaties protecting common goods are sufficiently equivalent to human rights conventions, which also bind belligerents during armed conflict (see above para 9). According to this line of reasoning it seems convincing to add a third category of environmental treaties which remain in force during armed conflict: treaties governing the use and protection of shared natural resources—international watercourses, rivers, and lakes—if and only if these treaties seek to protect an environmental good in the common interest of the State Community as a whole (Vöneky [2001] 215 et seq; for a broader approach Art 5 Annex (g) ILC Draft Articles). The ICJ in its advisory opinion on the Legality of the Threat or Use of Nuclear Weapons avoided answering the question whether and to what extent peacetime treaties relating to the protection of the environment are applicable between belligerent States (at para 30 et seq) and concluded only that peacetime environmental law is not the ‘most directly relevant applicable law’ during an armed conflict (at para 34).

6.  Ius Cogens Rules and Erga Omnes Obligations

11  Finally, rules which are part of ius cogens or are obligations erga omnes seem to be generally accepted as remaining in force during armed conflicts for belligerent States (Chinkin 188; Vöneky [2001] 290 et seq). In more general terms this is stressed by the ILC Draft Articles that state: ‘The termination of or the withdrawal from a treaty, or the suspension of its operation, as a consequence of an armed conflict, shall not impair in any way the duty of any State to fulfil any obligation embodied in the treaty to which it would be subject under international law independently of that treaty’ (Art 9 ILC Draft Articles).

C.  Exceptions and Derogations

12  Having stated that several types of peacetime treaties and other provisions of peacetime international law continue to apply between belligerent States, it is necessary to consider the extent to which these treaties bind belligerent States. It cannot be doubted that if peacetime standards bind parties during an armed conflict in the same way as during peacetime, the duty to fulfil these treaties would hardly be realistic. Although it is beyond the scope of this entry to examine this problem in depth, some general comments may be made in respect of the possibilities for modifying peacetime obligations generally applying to belligerents due to the extraordinary circumstances of an armed conflict.

13  In legal doctrine, there are four dominant approaches regarding the limitation of peacetime treaty obligations in cases of armed conflict. These are: (1) express derogation clauses; (2) inherent limitations of the treaty concerned; (3) justifications recognized in the law of State responsibility, particularly the state of necessity; and (4) general principles of international law relating to the suspension and termination of treaties.

1.  Express Derogation Clauses

14  First of all, it is not doubtful that if a peacetime treaty entails special derogation clauses for emergency situations or armed conflicts—as do the major human rights treaties—these clauses must be applied (eg Art 4 International Covenant on Civil and Political Rights [1966]; Art 15 European Convention for the Protection of Human Rights and Fundamental Freedoms [1950]). Other peacetime treaties, as, for instance, environmental treaties, rarely entail such express derogation clauses (but see Art XVII African Convention on the Conservation of Nature and Natural Resources). Some peacetime treaties do not entail general derogation clauses, but have clauses allowing deviations from particular obligations because of urgent national interests (Art 9 (1) Convention on the Conservation of European Wildlife and Natural Habitats; Art III (5) (d) Convention on the Conservation of Migratory Species of Wild Animals; Art 2 (5) Convention on Wetlands of International Importance especially as Waterfowl Habitat). Other provisions permit State Parties to not fulfil certain information duties in case the transfer of information could affect national security (Art 8 Convention on the Protection and Use of Transboundary Watercourses and International Lakes; Art 18 (1) Convention on the Protection of the Marine Environment of the Baltic Sea Area; Art 9 (3) Convention for the Protection of the Marine Environment of the North-East Atlantic; Art 12 (5) Convention on Co-operation for the Protection and Sustainable Use of the River Danube; similar as well Art 302 UN Convention on the Law of the Sea).

2.  Inherent Treaty Limitations

15  The second approach applies to treaties where express derogation clauses are missing but the obligations can be modified by reference to inherent limitations. For example, some commentators assert that Art 2 (1) and (4) International Covenant on Economic, Social and Cultural Rights (1966) recognizes that the extraordinary circumstances of an armed conflict can modify the standards and obligations for protecting human rights (Kälin and Gabriel 23 et seq, 83). This technique for modifying the peacetime standards can be applied to other peacetime treaties where the fulfilment of an obligation is linked to the ‘particular conditions and capabilities’ of the States or where the duties are only to be fulfilled ‘as far as possible and appropriate’ (eg Art 194 (1) UN Convention on the Law of the Sea).

3.  Justifications Recognized in the Law of State Responsibility

16  The third and most important approach to modify peacetime standards is to rely on the justifications recognized under the general international law of State responsibility. If the conditions of one of the justifications are met by the circumstances of an international armed conflict, a State cannot be responsible for the injury of a peacetime treaty obligation. Justification on grounds of self-defence, countermeasures in respect of an internationally wrongful act, and necessity are especially relevant during international armed conflicts. The ILC Draft Articles state in this regard ‘[a] State exercising its right of individual or collective self-defence in accordance with the Charter of the United Nations is entitled to suspend in whole or in part the operation of a treaty incompatible with the exercise of that right’ (Art 13 ILC Draft Articles). However, concerning the justification on grounds of self-defence it is questionable whether every State that is a victim of an act of aggression or claims on justified grounds to be such a victim can refer to this justification. One could argue that it would be contrary to the principle that during an armed conflict there is no difference between the aggressor State and the victim State in regard to the international rules regulating the conduct of hostilities. Hence, it seems to be preferable to opine that a State can only refer to the justification of self-defence in breaching peacetime treaties if this justifies a reaction to a specific breach of the ius in bello of the other State Party; this would mean that not only the victim of an aggression but also the aggressor State could in principle refer to the justification of self-defence in regard to specific military actions (Vöneky [2001] 480). The ICJ in its advisory opinion on the Legality of the Threat or Use of Nuclear Weapons draws the threshold at the deprivation of the right of self defence and concludes rather imprecisely: ‘The Court does not consider that the [peacetime environmental] treaties in question could have intended to deprive a State of the exercise of its right of self-defence under international law … ’ (para 30). It has to be noted, as well, that the most important justification during armed conflict—a state of necessity—is strictly limited to cases where non-compliance is necessary and proportional.

4.  General Principles Relating to the Suspension and Termination of Treaties

17  A fourth approach considers the general principles of international law relating to suspension and termination of treaties on grounds of a material breach, supervening impossibility of performance, and fundamental change of circumstances (see Art 17 ILC Draft Articles; Ipsen 1050 et seq; Tarasofsky 65 et seq). These principles apply at least to the same extent during international armed conflict as during peacetime, since belligerent States shall not be given fewer possibilities to suspend their treaty obligations than contracting parties in peacetime. These general principles also entail several limitations. For instance it is generally acknowledged that a material breach cannot be invoked to suspend or terminate peremptory norms of international law (Art 60 (5) VCLT); an impossibility of performance and a fundamental change of circumstances may not be invoked when it is the result of a breach of an international obligation by the party invoking the ground (ibid; Arts 61 (2), 62 (2) VCLT). As a breach of the ius ad bellum constitutes such a breach of an international obligation, an aggressor State cannot terminate or suspend peacetime treaty obligations by claiming impossibility of performance or fundamental change of circumstances (Vöneky [2001] 222); even in broader terms the ILC Draft Articles emphasise that ‘[a] State committing aggression within the meaning of the Charter of the United Nations and GA Res. 3314 (XXIX) of the General Assembly of the United Nations shall not terminate, withdraw from, or suspend the operation of a treaty as a consequence of an armed conflict of the effect would be to the benefit of that State’ (Art 15 ILC Draft Articles).

D.  Conclusion

18  Since the end of World War II the international legal order seeks to promote peace and peaceful relations between States; because of this it seems prima facie convincing that peacetime obligations bind States during an armed conflict if there are not compelling reasons that speak against the application. However, looking at State practice it can be shown that the question of the effect of an armed conflict on treaties is still in many parts one of the most unsettled and complicated topics in international law. The discussions in the ILC show that there are several questions which are highly controversial in regard to the effect of armed conflicts on peacetime treaties. Nevertheless, as elaborated above, there is a trend towards an increasing application of peacetime treaties: at least some categories of peacetime treaties and rules remain per se applicable even if the obligated States take part in an armed conflict (paras 5–11 above). This does not exclude belligerent States from modifying these peacetime standards which are applicable during armed conflict (paras 12–17 above), but in the end there do exist ‘core obligations’ of peacetime law; these are defined by the peremptory norms, and the limitations of necessity and proportionality, and they provide a fruitful approach for determining the core standards applicable during an armed conflict on a case-by-case basis. Looking from a broader perspective, the development of the last decades seems to indicate that there may be a paradigm shift in the future: then it will be necessary that each State must give convincing reasons why a certain peacetime obligation cannot be fulfilled because of an armed conflict.

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