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  • Jutta Brunnée (a1) and Stephen J Toope (a2)


Can a few primarily Western States expand the right to self-defence against non-State actors, incorporating the unwilling or unable standard? Even on a traditional reading of customary law formation, the answer is no because proponents have failed to attract consistent and widespread support. What is more, using our interactional international law approach, we show that efforts to date have not been successful because they have failed to address fundamental rule of law concerns. The current state of world politics has perhaps caught proponents of the unwilling or unable standard in a difficult bind. We suggest how proponents might carefully develop the law on self-defence against non-State actors.

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1 The concept of ‘norm entrepreneurship’—self-conscious attempts by international actors including States to create, shift or destroy norms, including legal norms—is well established in the literature of international relations. See eg Finnemore, M and Sikkink, K, ‘International Norm Dynamics and Political Change’ (1998) 52 IntlOrg 887 ; and Checkel, JT, ‘The Constructivist Turn in International Relations Theory’ (1998) 50 World Politics 324 .

2 See Corfu Channel Case (United Kingdom of Great Britain and Northern Ireland v Albania) [1949] ICJ Rep 22. And see Christakis, T, ‘Challenging the “Unwilling or Unable” Test’ (2017) 77 Heidelberg Journal of International Law 19 , 20 (noting that the ‘unwilling or unable’ standard ‘profoundly alters the nature of the due diligence principle’).

3 See Frowein, JA, ‘Article 51 and the Realities of the Present Day World’ (2017) 77 Heidelberg Journal of International Law 47 , 48 (arguing that ‘attribution to the state from whose territory the armed attack is being launched is [not] necessary’). And see Tsagourias, N, ‘Self-Defence against Non-State Actors: The Interaction between Self-Defence as a Primary Rule and Self-Defence as a Secondary Rule’ (2016) 29 LeidenJIL 801 , 808–9 (noting that the unwilling or unable test ‘moves away from attribution and recognizes non-state actors as independent authors of armed attacks – and direct targets of self-defence – even if such action takes place on the territory of the host state’). More generally, see Kreß, C, ‘Some Reflections on the International Legal Framework Governing Transnational Armed Conflicts’ (2010) 15 Journal of Conflict & Security Law 245 , at 248 (arguing that ‘Article 51 of the UN Charter enshrines a right to self-defence against armed attacks carried out by non-State actors even when those acts cannot be attributed to the host state.’); and Gewaltverbot und Selbstverteidigungsrecht nach der Satzung der Vereinten Nationen bei staatlicher Verwicklung in Gewaltakte Privater (Duncker & Humblot 1995). Other authors have strongly rejected this assessment. See eg Nolte, G and Randelzhofer, A, ‘Article 51’ in Simma, B et al. (eds), The Charter of the United Nations: A Commentary, Vol II, 3rd edn (Oxford University Press 2012) 1397 , at 1414–19 (arguing that attacks by non-State groups are not armed attacks within the meaning of Article 51).

4 See eg A Deeks, ‘“Unwilling or Unable”: Toward a Normative Framework for Extraterritorial Self-Defense’ (2012) 52 VaJIntlL 483, 486–8; T Ruys and L Ferro, ‘Divergent Views on the Content and Relevance of the Jus ad Bellum in Europe and the United States? The Case of the U.S.-Led Military Coalition against “Islamic State”’ (10 February 2016) <> 8. See also Trapp, KN, ‘Back to Basics: Necessity, Proportionality, and the Right of Self-Defence against Non-State Terrorist Actors’ (2007) 56 ICLQ 141 (arguing that, as in all claims of self-defence, in relation to non-State actors the key conditions are necessity and proportionality).

5 Lubell, N, ‘Fragmented Wars: Multi-Territorial Military Operations against Armed Groups’ (2017) 93 International Law Studies 215 , 219–20 (footnotes and a fictional scenario removed from quote).

6 See text accompanying notes 87–88.

7 Brunnée, J and Toope, SJ, ‘The Use of Force: International Law after Iraq’ (2004) 53 ICLQ 785 .

8 See Brunnée, J and Toope, SJ, Legitimacy and Legality in International Law: An Interactional Account (Cambridge University Press 2010); Brunnée, J and Toope, SJ, ‘Interactional International Law and the Practice of Legality’ in Adler, E and Pouliot, V (eds), International Practices (Cambridge University Press 2011) 108 ; and Brunnée, J and Toope, SJ, ‘Interactional Legal Theory, the International Rule of Law and Global Constitutionalism’ in Lang, A and Wiener, A (eds), Handbook of Global Constitutionalism (Edward Elgar Publishers 2017) 170 .

9 In the Obama Administration's last official statement on the law of self-defence, the White House notes a third category of allowable force: ‘use of force in an otherwise lawful manner with the consent of the territorial State’. US, White House, ‘Report on the Legal and Policy Frameworks Guiding the United States’ Use of Military Force and Related National Security Operations’ (2016) <> 8. See also Tsagourias (n 3) 809 (observing that ‘self-defence and consensual intervention are independent bases for the use of force in international law’). The ‘consensual intervention’ category does not apply in the Syrian case.

10 Other key debates, which we leave aside for present purposes, concern necessity and proportionality in the exercise of the right to self-defence. Gardham, J, Necessity, Proportionality and the Use of Force by States (Cambridge University Press 2004).

11 We use ‘IS’ as shorthand for the various manifestations of the terror network also known as the ‘Islamic State in Iraq and the Levant’ (ISIL) or ‘Da'esh.’

12 Gray, C, International Law and the Use of Force (3rd edn, Oxford University Press 2008) 6 ; and Corten, O, The Law Against War: The Prohibition on the Use of Force in Contemporary International Law (Hart Publishing 2010) 126 , 161.

13 Trapp, K, ‘Actor-Pluralism, the “Turn to Responsibility” and the jus ad bellum: “Unwilling or Unable” in Context’ (2015) 2 Journal on the Use of Force and International Law 199 , 205. Note that the United States now holds that no State involvement is required for an attack to to qualify as an armed attack triggering the right to self-defence. See US, Department of Defense – Office of the General Counsel, ‘Law of War Manual’ (June 2015, updated December 2016) <> 47 (‘The inherent right of self-defense, recognized in Article 51 of the Charter of the United Nations, applies in response to any “armed attack,” not just attacks that originate with States.’).

14 Ruys, T, ‘Armed Attack’ and Article 51 of the UN Charter: Evolutions in Customary Law and Practice (Oxford University Press 2010) 400–1.

15 ibid 402–4.

16 United Nations General Assembly, Res 3314 (XXIX), ‘Definition of Aggression’ (14 December 1974) UN Doc A/RES/3314 (XXIX).

17 Ruys (n 14) 131–2, 386–90.

18 Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) [1984] ICJ Rep 392.

19 ibid [109], [195].

20 For a discussion of the ICJ's approach, see Tsagourias (n 3) 814–18.

21 See Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory (Advisory Opinion) [2004] ICJ Rep 163; Case Concerning Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) [2005] ICJ Rep 116. And see Case Concerning Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v Serbia and Montenegro) [2007] ICJ Rep 43.

22 Ruys (n 14) 421–33. Tibori-Szabó suggests that Iran also invoked the unwilling or unable standard to justify defensive action against Kurdish strongholds in Iraq. Tibori-Szabó, K, ‘The “Unwilling or Unable” Test and the Law of Self-Defence’ in Paulussen, C et al. . (eds), Fundamental Rights in International and European Law: Public and Private Law Perspectives (Springer 2015) 79 , 95.

23 See UN Security Council (UNSC) Res 1368 (12 September 2001) UN Doc S/RES/1368; UNSC Res 1373 (28 September 2001) UN Doc S/RES/1373.

24 See UNSCOR, 56th Year, UN Doc S/2001/946; and UNSCOR, 56th Year, UN Doc S/2001/947.

25 Tibori-Szabó (n 22) 86.

26 AE Kramer and A Barnard, ‘Russian Soldiers Join Syria Fight’ The New York Times (5 October 2015) <>.

27 US, White House, ‘Statement by the President on Airstrikes in Syria’ (23 September 2014) <>.

28 UNSCOR, 69th Year, UN Doc S/2014/695.

29 UNSCOR 70th Year, UN Doc S/2015/221.

30 UNSCOR 70th Year, UN Doc S/2015/745.

31 Ruys and Ferro (n 4) 6.

32 ibid 11–12. And see P Starski, ‘Silence within the Process of Normative Change and Evolution of the Prohibition on the Use of Force – Normative Volatility and Legislative Responsibility’ (2016) Max Planck Institute for Comparative Public Law & International Law (MPIL) Research Paper No 2016-20 <> 30; Flasch, O, ‘The Exercise of Self-Defence against ISIL in Syria: New Insights on the Extraterritorial Use of Force against Non-State Actors’ (2016) 3 Journal on the Use of Force and International Law 37 , 63.

33 UNSCOR, 69th Year, UN Doc S/2014/851 (2014).

34 ibid.

35 Flasch (n 32) 60 (discussing the statements of Bahrain, Jordan, Saudi Arabia and the United Arab Emirates).

36 Starski (n 32) 31–2.

37 UN SC Res 2249 (20 November 2015) UN Doc S/Res/2249, preamble.

38 ibid para 5 (emphasis added). See text accompanying notes 42–48 for a discussion of the significance of linking any right to self-defence to the territorial control exercised by non-State actors.

39 UNSCOR, 70th Year, 7565th Mtg, Un Doc S/PV.7565 (2015) at 2.

40 See UK, HC, Parliamentary Debates, vol 602, col 1489, 1491 (Prime Minister's Statement 26 November 2015) <>; and UK, ‘Prime Minister's Response to the Foreign Affairs Select Committee's Second Report of Session 2015-16: The Extension of Offensive British Military Operations to Syria’ (November 2015) <>.

41 UNSCOR, 70th Year, UN Doc S/2015/928.

42 See D Akande and M Milanovic, ‘The Constructive Ambiguity of the Security Council's ISIS Resolution’ (EJIL: Talk!, 21 November 2015) <>. And see M Wood, ‘The Use of Force in 2015 with Particular Reference to Syria’ (2016) Hebrew University of Jerusalem Legal Studies Research Paper Series 16-05 <>.

43 UNSCOR, 70th Year, UN Doc S/2015/946. Interestingly, in the justification brought forward by the German government to the Bundestag, there is a reference to military self-defence measures being undertaken in Syria by States allied with Germany ‘because the Syrian government is unable/or unwilling to suppress the IS attacks emanating from its territory’ (at 2). The statement appears to be descriptive, but could be read as an endorsement—except that it goes on to refer to UN Security Council Resolution 2249 and specifies that ‘the deployment of German forces occurs primarily in and above the operational area of the terror organization IS in Syria, and in the territory of states from which a permission has been obtained from the relevant government … ’ (at 3). These statements seem to align with the position subsequently taken in the German letter to the Security Council. Federal Republic of Germany. Deutscher Bundestag. Drucksache 18/6866 (1 December 2015) [translation by Brunnée].

44 UNSCOR, 71st Year, UN Doc S/2016/523.

45 von Bernstorff, J, ‘Drone Strikes, Terrorism and the Zombie: On the Construction of an Administrative Law of Transnational Executions’ (2016) 5(7) European Society of International Law (ESIL) Reflections <>. But see Urs, P, ‘Effective Territorial Control by Non-State Armed Groups and the Right to Self-Defence’ (2017) 77 Heidelberg Journal of International Law 31 , 33 (suggesting that the argument is unpersuasive because ‘it is not rooted in the attribution of responsibility’). Other commentators have argued that it is not clear that Syria is ‘unwilling’ to act, given that it has launched military strikes against IS and has invited Russia into its territory to combat IS. It is also not clear that lack of territorial control necessarily proves ‘inability’ to act; in the same way as external actors, the State could simply launch attacks on the territory that it no longer controls. Sjöstedt, B, ‘Applying the Unwilling/Unable State Doctrine – Can a State be Unable to Take Action?’ (2017) 77 Heidelberg Journal of International Law 39 , 41. And see Ruys and Ferro (n 4) 10. Obviously, there are circumstances where ‘failed States’ are genuinely unable to act.

46 M Hakimi and J Katz Cogan, ‘A Role for the Security Council on Defensive Force?’ (2016) EJIL: Talk! <>.

47 ibid.

48 UNSCOR, 71st Year, UN Doc S/2016/34 (Denmark); UNSCOR, 71st Year, UN Doc S/2016/132 (Netherlands); UNSCOR, 71st Year, UN Doc S/2016/513 (Norway).

49 Hakimi, M, ‘Defensive Force against Non-State Actors: The State of Play’ (2015) 91 International Law Studies 1 , 19.

50 Wood (n 42) 1 and Kreß (n 3). But see, for a more equivocal assessment, Ruys and Ferro (n 4) 8–9, and for a complete rejection of the argument, Nolte and Randelzhofer (n 3).

51 See Becker-Lorca, A, ‘Rules for the “Global War on Terror”: Implying Consent and Presuming Conditions for Intervention’ (2012) 45 NYUJIntlLaw&Pol 1 , 36–9. Kammerhofer, J, ‘Positivism’ in Carthy, A (ed), Oxford Bibliographies: International Law (Oxford University Press 2015) 56 . And Tibori-Szabó (n 22) 86.

52 See Hakimi (n 49); Hakimi and Katz Cogan (n 46); and Starski (n 32).

53 E Chachko and A Deeks, ‘Who is on Board with “Unwilling and Unable”?’ (10 October 2016) Lawfare <>.

54 But see Ruys and Ferro (n 4) 19, reading the German letter as ‘a (barely concealed) reference’ to the unwilling or unable standard.

55 See UK, D Cameron, ‘PM Statement Responding to FAC Report on Military Operations in Syria’ (26 November 2015) <>; and UK, D Cameron, ‘Response to the Foreign Affairs Select Committee's Second Report of Session 2015-16: The Extension of Offensive British Military Operations to Syria’ (November 2010) <>.

56 See UNSCOR, 69th Year, UN Doc S/2014/851; UNSCOR, 70th Year, UN Doc S/2015/688; and UNSCOR, 70th Year, UN Doc S/2015/928.

57 US (n 9) 10.

58 ibid 52.

59 See also Christakis (n 2) 18 (citing a 2016 oral statement by the head of the legal office of the French Ministry of Foreign Affairs, indicating scepticism regarding the ‘unwilling or unable’ standard). But see Ruys and Ferro (n 4) 13 (citing the French Foreign Minister as stating that there were no legal impediments to strikes in Syria on the basis of Article 51). However, judging from published comments by the French Foreign Office Legal Adviser, France too seems to emphasize the exceptional circumstances involving the Security Council's recognition of the peace and security threat posed by IS, and its resources and territorial control. See Alabrune, F, ‘Fondements juridiques de l'intervention militaire française contre Daech en Irak et en Syrie’ (2016) 120 Revue générale de droit international public 41 .

60 Canada, Office of the Prime Minister, ‘Prime Minister Sets New Course to Address Crises in Iraq and Syria and Impacts on the Region’ (8 February 2016) <>.

61 Chachko and Deeks (n 53) 19 (referring to a Russian Foreign Ministry statement on the illegality of US strikes in Syria). See also Ruys and Ferro (n 4) 9–10 (citing objections to the strikes in Syria by Russia, Iran, Cuba, Venezuela and Syria).

62 US (n 9) 10.

63 Chachko and Deeks (n 53) 19.

64 Non-Aligned Movement (NAM), 17th Summit of Heads of State and Government of the Non-Aligned Movement, Final Document (17–18 September 2016) NAM 2016/CoB/DOC.1. Corr.1 <> para 25.2.

65 See G Keinan, ‘Humanising the Right to Self-Defence’ (2017) 77 Heidelberg JIL 57 (stating that the “unable or unwilling” test is “backed by decades-long practice”). [This author is a member of the Military Advocate General’s Corps of the Israeli Defence Forces, writing in his personal capacity.] And see M Wood, ‘Self-Defence Against Non-State Actors – A Practitioner’s View’ (2017) 77 Heidelberg JIL 75, 76 (stating that “there is considerable support in State practice and writings for the ‘unwilling or unable’ test” but citing a list of authors, which authors, in turn, identify the practice of only three states as unequivocal – see Deeks (n 4). [Wood is a former UK Foreign Office Legal Advisor; he cites a former Assistant Legal Advisor in the US Department of State (Deeks (n 4)), a former UK Foreign Office Deputy Legal Advisor who coordinated a study on the law of self-defence (E Wilmshurst, ‘The Chatham House Principles of International Law on the Use of Force in Self-Defence’ (2006) 55 ICLQ 963), another former UK Foreign Office Legal Advisor who, in a private capacity but informed by operational experience, compiled principles of self-defence against non-state actors (D Bethlehem, ‘Self-Defence Against an Imminent or Actual Armed Attack by Nonstate Actors’ (2012) 106 AJIL 770), and the ‘Leiden Policy Recommendations on Counter-terrorism and International Law’ (2010) 57 NILR 531 (a set of policy recommendations produced through a consultative process involving three expert working groups; the group on ‘the use of force against terrorists’ was co-chaired by Wood and included Wilmshurst). Wood has written extensively on the use of force against non-state actors. While his writing notes increasing international support for the unwilling or unable standard, he also averts to the caution warranted in equating the Chatham House and Bethlehem Principles with evidence of state practice or opinio juris. See e.g. M Wood, ‘The Law on the Use of Force: What Happens in Practice?’ (2013) 53 Indian JIL 345, 356. See also E Wilmshurst and M Wood, ‘Self-Defence Against Nonstate Actors: Reflections on the “Bethlehem Principles”’ (2013) 107 AJIL 390, 393, 395 (noting the proposals involving the unwilling or unable standard ‘remain controversial,’ even if they are ‘rightly’ cast as ‘increasingly accepted’).

The overall tenor of academic commentary is mixed, but it is important to note that many scholars conclude that the unwilling or unable standard has not become part of customary law. See, e.g., M Hakimi, ‘Defensive Force against Non-State Actors: The State of Play’ (2015) 91 Int’l L. Studies 1, 30-1; O Corten, ‘The “Unwilling or Unable” Test: Has it Been, and Could it be, Accepted?’ (2016) 29 Leiden JIL 777, 799; ME O’Connell, ‘Dangerous Departures’ (2013) 107 AJIL 380, 384; N Tzouvala, ‘TWAIL and the “Unwilling or Unable” Doctrine: Continuities and Ruptures’ (2016) 109 AJIL Unbound <“unwilling-or-unable”-doctrine> accessed 28 July 2017, 266; Tibori-Szabó (n 22) 92-3; and T Christakis (n 2) 22.

66 See eg United Kingdom, Attorney General Speech at International Institute for Strategic Studies: ‘The Modern Law of Self-Defence’ (11 January 2017) <>.

67 Chachko and Deeks (n 53) 11–12.

68 Even Daniel Bethlehem's much-quoted ‘Principles’ concerning self-defence against non-State actors are acknowledged not to ‘purport to reflect a settled view of the law or the practice of any state’; rather, they are intended to suggest what ‘the appropriate principles are and ought to be’. Bethlehem, D, ‘Self-Defense against Imminent or Actual Armed Attack by Nonstate Actors’ (2012) 106 AJIL 770 , 770 and 775 (the Principles appear at 775–7).

69 See Corten (n 12) 785–91; Starski (n 32); and Tibori-Szabó (n 22) 86. See also Deeks (n 4) 549–50 (providing a list of relevant State practice between 1817 and 2011, identifying only Israel, Turkey and the United States as having ‘specifically invoked the “unwilling or unable” test or a closely related concept’; the UK is listed as well, but only for its argumentation in the context of the Caroline incident).

70 Three NAM-members, Bahrain, Jordan, and the United Arab Emirates, have supported or participated in the strikes against IS, endorsing a self-defence rationale. However, they have not endorsed the unable or unwilling standard. See Flasch (n 32) 64.

71 See text accompanying note 83.

72 von Bernstorff (n 45) 3.

73 See Brunnée and Toope, Legitimacy and Legality (n 8); and Brunnée and Toope, ‘Interactional International Law’ (n 8).

74 See Postema, GJ, ‘Implicit Law’ (1994) 13 Law and Philosophy 361 . Reprinted in Witteveen, WJ and van der Burg, W (eds), Rediscovering Fuller: Essays on Implicit Law and Institutional Design (Amsterdam University Press 1999) 255 . And Reinold, T and Zürn, M, ‘“Rules about Rules” and the Endogenous Dynamics of International Law: Dissonance Reduction as a Mechanism of Secondary Rule-Making’ (2014) 3 Global Constitutionalism 236 .

75 Fuller, LL, The Morality of Law (revised edn, Yale University Press 1969). Fuller proposed eight criteria (generality, promulgation, non-retroactivity, clarity, non-contradiction, not requiring the impossible, relative constancy over time, and congruence between legal norms and the actions of officials operating under the law). In this discussion, we will address only some of them.

76 Brunnée and Toope, ‘Interactional Legal Theory’ (n 8).

77 See Ahmed, DI, ‘Defending Weak States against the “Unwilling or Unable” Doctrine of Self-Defense’ (2013) 9 Journal of International Law and International Relations 1 ; and Tzouvala (n 65).

78 Von Bernstorff (n 45) 4.

79 Becker-Lorca (n 51).

80 Tzouvala (n 65) 2.

81 Tibori-Szabó (n 22) 89.

82 ibid 95.

83 North Sea Continental Shelf cases (Germany v Denmark, Germany v Netherlands) [1969] ICJ Rep 3 [73]–[74]. Our interactional approach to international law suggests that opinio juris is best understood as the need to test subsequent practices surrounding a given legal norm against the criteria of legality. Put differently, continuing practices of legality are evidence of opinio juris. See Brunnée and Toope, Legitimacy and Legality (n 8) 47–8.

84 Brunnée, J, ‘Sources of International Environmental Law: Interactional Law’ forthcoming in Besson, S and d'Aspremont, J (eds), Oxford Handbook on the Sources of International Law (Oxford University Press 2017).

85 See eg Wilmshurst, E, Principles of International Law on the Use of Force by States in Self-Defence (Chatham House 2005) 2 , 12.

86 Supporters of the unwilling or unable standard accept that the possibility of objective assessment is required to buttress the standard's legal status. See Bethlehem (n 68) 776 [Principles 11 and 12].

87 Chayes, A, The Cuban Missile Crisis (Oxford University Press 1974) 65 . Although not the focus of this article, the concern over the proper scope of ‘imminence’ is very much alive, witness the pre-occupations of two senior legal advisors. See UK Attorney General Speech (n 66); and the Australian Attorney-General, George Brandis, ‘The Right to Self-Defence against Imminent Attack in International Law’ (Lecture delivered at the T C Beirne School of Law, University of Queensland, 11 April 2017) <> (speaking to a Law School audience).

88 See Ahmed (n 77) 14–16; Becker-Lorca (n 51) 92; Deeks (n 4) 488; Bethlehem (n 68) 584; and Tibori-Szabó (n 22) 88.

89 Brandis (n 87).

90 Chayes (n 87) 65.

91 Von Bernstorff (n 45) 2, 6.

92 Becker-Lorca (n 51) 91–92.

93 ibid 90, 93.

94 See eg Scharf, M, ‘How the War against ISIS Changed International Law’ (2016) 48 CaseWResJIntlL 15 .

95 Becker-Lorca (n 51) 13.

96 See also Wood, ‘The Law on the Use of Force’ (n 65) 365 (cautioning that ‘[e]fforts radically to amend or reinterpret the rules are neither desirable, nor likely to succeed. One or a few States, however powerful, cannot change established rules of international law, Charter-based ones at that’.)

97 As it turns out any such sense has proved to be well-founded. See eg K Beckerle, ‘U.S. Officials Risk Complicity in War Crimes in Yemen’ (Just Security, 4 May 2017) <>; M Milanovic, ‘The Clearly Illegal US Military Strike in Syria’ (EJIL: Talk!, 7 April 2017) <>; K Tibori-Szabó, ‘The Downing of the Syrian Fighter Jet and Collective Self-Defence’ (Opinio Juris, 23 June 2017) <>.

98 Brandis (n 87). See also UK Attorney General Speech (n 66) 21–2.

99 UNGA, World Summit Outcome Document, UN Doc A/Res./60/1 (2005) para 79. See also, Brunnée and Toope, Legitmacy and Legality (n 8) Ch 6.

100 See eg, Y Kawashima (updated by A Sanders-Zakre), ‘Timeline of Syrian Chemical Weapons Activity, 2012-2017’ (Arms Control Association, 7 April 2017) <>; and K Calamur, ‘How Is Syria Still Using Chemical Weapons?’ (The Atlantic, 4 April 2017) <>.

We thank Professors Eyal Benvenisti, Harold Koh and Georg Nolte for their critical readings of a draft. Of course, the authors alone are responsible for the views expressed, and for any errors or infelicities.

(Most of the work for this article was undertaken while serving as Director of the Munk School of Global Affairs, University of Toronto.)


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