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The invocation of the right to self-defence in response to armed attacks conducted by armed groups: Implications for attribution

Published online by Cambridge University Press:  01 March 2019

Erika de Wet
Erika de Wet*
Affiliation:
BIur, LLB, LLD (University of the Free State); LLM (Harvard); Habilitationsschrift (Zurich); SARChI Professor of International Constitutional Law, University of Pretoria, South Africa; Honorary Professor, University of Bonn, Germany
*
Email: [email protected]
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Abstract

The right to self-defence in Article 51 of the United Nations Charter is increasingly being invoked in response to armed attacks conducted by armed groups located in a territory of another state, with or without the (direct) assistance of such a state. This article examines the implications of the invocation of the right to self-defence under these circumstances for the principles of attribution within the jus ad bellum paradigm. First, it illuminates how the threshold requirements for indirect armed attacks (that is, the state acting through a private actor) have been lowered since the 1986 Nicaragua decision of the International Court of Justice. In so doing, the article suggests that in order to prevent a complete erosion of the benchmarks of an indirect armed attack, the notions of ‘substantial involvement’ in an armed attack, ‘harbouring’, and ‘unwillingness’ should be interpreted as manifestations of due diligence. Thereafter, the article illustrates that there is also an increasing attribution of armed attacks directly to non-state actors, notably those located in areas over which territorial states have lost control. Such states could be depicted as being ‘unable’ to counter the activities of non-state actors. The article further submits that particularly in these instances, the principle of necessity within the self-defence paradigm can play an important role in curbing the potential for abuse inherent in the vague notion of ‘inability’, if interpreted in light of Article 25 of the Articles on State Responsibility for Internationally Wrongful Acts.

Keywords

attributionconsentnecessityresponsibilityself-defence
Type
ORIGINAL ARTICLE
Information
Leiden Journal of International Law , Volume 32 , Issue 1 , March 2019 , pp. 91 - 110
Copyright
© Foundation of the Leiden Journal of International Law 2018 

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Footnotes

*

This research was supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Grant No 98338). All websites last visited on 8 August 2018.

References

1 The Charter of the United Nations of 26 June 1945, Art. 51, first sentence, determines that: ‘Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security.’ Full text available at treaties.un.org/doc/source/docs/charter-all-lang.pdf.

2 The extensive literature pertaining to the right to self-defence generated since the turn of the century includes Charney, J.I, ‘The Use of Force Against Terrorism and International Law’, (2001) 95 American Journal of International Law, at 836 ffCrossRefGoogle Scholar; Franck, T., ‘Terrorism and the Right to Self-Defence’, (2001) 95 American Journal of International Law, at 839 ffCrossRefGoogle Scholar; Brunnée, J. and Toope, S., ‘The Use of Force: International Law After Iraq’, (2004) 53 International and Comparative Law Quarterly, at 785 ffCrossRefGoogle Scholar; Brunnée, J. and Toope, S., ‘Self-Defence Against Non-state Actors: Are Powerful States Willing But Unable to Change the International Law?’, 2018 (67) International and Comparative Law Quarterly, at 263 ffCrossRefGoogle Scholar; Murphy, S., ‘Self-Defence and the Israeli Wall Advisory Opinion: An Ipse Dixit from the ICJ?’, (2005) 99 American Journal of International Law, at 62 ffCrossRefGoogle Scholar; Fletcher, G.P. and Ohlin, J.D., Defending Humanity. When Force is Justified and Why (2008), at 208–18Google Scholar; Tams, C.J., ‘The Use of Force Against Terrorists’, (2009) 20 European Journal of International Law, at 359 ffCrossRefGoogle Scholar; Ruys, T., ‘Armed Attack’ and Article 51 of the UN Charter (2010)CrossRefGoogle Scholar; van Steenberghe, R., ‘Self-Defence in Response to Attacks by Non-state Actors in the Light of Recent State Practice: A Step Forward?’, (2010) 23 LJIL, at 183 ffCrossRefGoogle Scholar; Bethlehem, D., ‘Principles Relevant to the Scope of a State’s Right of Self-Defence Against an Imminent or Actual Armed Attack by Non-State Actors’, (2012) 106 American Journal of International Law, at 769 ffGoogle Scholar; Randelzhofer, A. and Nolte, G., ‘Article 51’, in Simma, Bruno et al. (eds.), The Charter of the United Nations. A Commentary Vol. II (2012), at 1397 ffGoogle Scholar; Koh, H.H., ‘International Law in Cyberspace’, Opinio Juris, 18 September 2012, available at opiniojuris.org/2012/09/19/harold-koh-on-international-law-in-cyberspace/;Google Scholar Deeks, A., ‘“Unwilling or Unable”: Towards a Normative Framework for Extraterritorial Self-Defence’, (2012) 52 Virginia Journal of International Law, at 483 ffGoogle Scholar; Tladi, D., ‘The Nonconsenting Innocent State: The Problem with Bethlehem’s Principle 12’, (2013) 107 American Journal of International Law, at 572 ffGoogle Scholar; Hakimi, M., ‘Defensive Force against Non-state Actors: The state of Play’, (2015) 91 International Law Scholarship, at 1 ff.Google Scholar; van Steenberghe, R, ‘The Law of Self-Defence and the New Argumentative Landscape on the Expansionists’ Side‚ (2016) 29 LJIL, at 43 ffCrossRefGoogle Scholar; Starski, P., ‘Right to Self-Defence, Attribution and the Non-State Actor – Birth of the “Unable or Unwilling” Standard?’, (2015) 75 Heidelberg Journal of International Law, at 455 ffGoogle Scholar; Corten, O., ‘The “Unwilling or Unable” Test: Has it Been and Could It Be Accepted?’, (2016) 29 LJIL, at 777 ffCrossRefGoogle Scholar; 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 LJIL, at 801 ffCrossRefGoogle Scholar; and Lanovoy, V., ‘The Use of Force by Non-State Actors and the Limits of Attribution of Conduct’, (2017) 28 European Journal of International Law, at 563 ffCrossRefGoogle Scholar.

3 Other contested issues of self-defence which are not examined in this analysis notably include the gravity threshold that is implied by an armed attack, the temporal requirements attached to self-defence, as well as the intricacies pertaining to the relationship between the necessity and proportionality requirements.

4 Military and Paramilitary Activities in and Against Nicaragua (Nicaragua v. United States), Merits, Judgment of 27 June 1986, [1986] ICJ Rep. 14.

5 Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory, Advisory Opinion of 9 July 2004, [2004] ICJ Rep. 136, para. 129. According to the majority of the ICJ, Art. 51 of the UN Charter did not excuse Israel’s security barrier on the Palestinian territories, in part because Israel did not claim that it had been attacked by another state. A similar logic appeared in Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v. Uganda), Judgment of 19 December 2005, [2005] ICJ Rep. 168, para. 146. See also Hakimi, supra note 2, at 5; Tsagourias, supra note 2, at 804. See Tladi, supra note 2, at 572.

6 UNGA, Res. 3314 (XXIX), Definition of Aggression, UN Doc. A/RES/29/3314 (1974); Arts. 3(a) to 3(f) give examples of the type of actions undertaken by state organs that would amount to a direct act of aggression.

7 Nicaragua decision, supra note 4, para. 195; Democratic Republic of the Congo decision, supra note 5, para. 146. In fact, in practice the terms ‘act of aggression’ and ‘armed attack’ may be regarded as two sides of the same coin in that both generate from states, even though the Definition of Aggression, supra note 6, initially was intended to clarify the term ‘aggression’ in Art. 39 of the UN Charter. See Randelzhofer and Nolte, supra note 2, at 1407–8.

8 Definition of Aggression, supra note 6, Art. 3.

9 Tsagourias, supra note 2, at 805; Council of European Union, Independent International Fact-Finding Mission on the Conflict in Georgia (2009), vol. II, at 260, available at www.mpil.de/files/pdf4/IIFFMCG_Volume_II1.pdf.

10 Nicaragua decision, supra note 4, para. 195; Democratic Republic of the Congo decision, supra note 5, para. 146; Ruys, supra note 2, at 479 ff; Tsagourias, supra note 2, at 814; and Independent International Fact-Finding Commission, supra note 9, at 260.

11 Nicaragua decision, supra note 4, paras. 115, 195, 226–31; Tsagourias, supra note 2, at 815.

12 See Nicaragua decision, supra note 4, para. 205.

13 A fact criticized in the Dissenting Opinion of Judge Sir Robert Jennings, Nicaragua decision, supra note 4, at 543.

14 See Dissenting Opinion of Judge Sir Robert Jennings, Nicaragua decision, supra note 4, at 543; similarly, the Dissenting Opinion of Judge Schwebel, Nicaragua decision, supra note 4, at 268–9, 332 ff. See also Ruys, supra note 2, at 415 ff; Randelzhofer and Nolte, supra note 2, at 1415–16.

15 Tsagourias, supra note 2, at 816; Starski, supra note 2, at 472–3; Brunnee and Toope (Self-Defence), supra note 2, at 267.

16 Lanovoy, supra note 2, at 578 and 580.

17 ILC Draft Articles on Responsibility of States for Internationally Wrongful Acts with Commentaries, 2001 YILC, Vol. II; UN Doc. A/Res/56/83 (2001).

18 See UN Doc. S/PV.2292 (1981), paras. 54–5 (Israel), emphasizing in particular Lebanon’s inability to control the PLO. See also Deeks, supra note 2, at 486; Ruys, supra note 2, at 422–3.

19 UN Doc. S/PV. 4836 (2003), at 7 (Israel); Myre, G., ‘Attacks What It Calls a Terrorist Camp in Syria’, New York Times, 6 October 2003, available at www.nytimes.com/2003/10/06/world/mideast-turmoil-airstrike-israel-attacks-what-it-calls-terrorist-camp-syria.htmlGoogle Scholar.

20 UN Doc. S/PV.5498 (2016), at 3 (UNSG).

21 As also recognized by the UNSC in UN Doc. S/RES/1701 (2006), para. 3; see also Hakimi, supra note 2, at 9.

22 Ruys, supra note 2, at 449 ff.

23 This was subsequent to the Libyan attacks on the Rome and Vienna airports in 1985. See R. Reagan, ‘The President’s News Conference’, 7 January 1986, available at www.presidency.ucsb.edu/ws/index.php?pid=36812. The United States further relied on the harbouring doctrine after the al-Qaida bombings of its embassies in Kenya and Tanzania in 1998, when striking a pharmaceutical plant in Sudan allegedly used by al-Qaida for producing chemical weapons, as well as terrorist camps in Afghanistan. See Letter dated 20 August 1998 from the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, UN Doc. S/1998/780 (1998). See also M. Jackson, Complicity in International Law (2015), at 182; Ruys, supra note 2, at 426; Lanovoy, supra note 2, at 571.

24 Letter of the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, UN Doc. S/2001/946 (2001); see also Tsagourias, supra note 2, at 806.

25 Letter of the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, UN Doc. S/2001/946 (2001); see also Gray, C., ‘Limits to the Use of Force’, 2014 (376) Collected Courses of The Hague Academy of International Law, at 138–9.Google Scholar

26 Letter dated 11 September 2002 from the Permanent Representative of the Russian Federation to the United Nations addressed to the Secretary-General, UN Doc. S/2002/1012, Ann. (2002), at 2, 3. Furthermore, Russia also invoked Art. 51 of the UN Charter in 1993, when engaging in extensive military action against non-state actors operating from and supported by Afghanistan. See Letter dated 15 July 1993 from the Permanent Representative of the Russian Federation addressed to the Secretary-General, UN Doc. S/26110, Ann. (1993), at 2, 3; see also Jackson, supra note 23, at 183; Deeks, supra note 2, at 486.

27 V. Putin [translated transcript of televised remarks on 4 September 2004], ‘Putin Tells the Russians: “We Shall Be Stronger”’, New York Times, 5 September 2004, available at www.nytimes.com/2004/09/05/world/europe/putin-tells-the-russians-we-shall-be-stronger.html.

28 ‘Russia to Launch Beslan Inquiry’, BBC News, 10 September 2004, available at news.bbc.co.uk/2/hi/europe/3645022.stm; see also Hakimi, supra note 2, at 9.

29 See African Union Non-Aggression and Common Defence Pact of 1 January 2005, Art. 1(c)(xi), available at au.int/en/treaties/african-union-non-aggression-and-common-defence-pact. See also Hakimi, supra note 2, at 9.

30 Status of ratification, available at au.int/sites/default/files/treaties/7788-sl-african_union_non-aggression_and_common_defence_pact.pdf.

31 UNGA Res. 2625 (XXV). Declaration on Principles of International Law Concerning Friendly Relations and Co-Operation Among States in Accordance with the Charter of the United Nations, UN Doc. A/RES/25/2625, Ann. (1970). The customary status of the Resolution has been confirmed in the Nicaragua decision, supra note 4, para. 191 and Democratic Republic of the Congo decision, supra note 5, para. 162.

32 Tsagourias, supra note 2, at 818.

33 Lanovoy, supra note 2, at 572.

34 Pact of the League of Arab States of 22 March 1945, Art. 6, 70 UNTS 241, available at treaties.un.org/pages/showDetails.aspx?objid=080000028015a44b; see also Zamani, M. and Nikouei, M., ‘Intervention by Invitation, Collective Self-Defence and the Enigma of Effective Control’, (2017) 16 Chinese Journal of International Law, at 24 and 25CrossRefGoogle Scholar.

35 Treaty of Joint Defence and Economic Co-operation Between the States of the Arab League of 17 June 1950, Art. 2, available at avalon.law.yale.edu/20th_century/arabjoin.asp.

36 Identical letters dated 26 March 2015 from the Permanent Representative of Qatar to the United Nations addressed to the Secretary-General and the President of the Security Council, Ann., UN Doc. S/2015/217 (2015), at 4–5; see also Ruys, T. and Ferro, L., ‘Weathering the Storm: Legality and Legal Implications of the Saudi-Led Military Intervention in Yemen’, (2016) 65 International and Comparative Law Quarterly, at 71CrossRefGoogle Scholar.

37 Statement by Mr Alyemany, Permanent Representative of Yemen to the UN, noting that Iran is the promotor of the coup, as well as the instigator of the sedition in Yemen. See UN Doc. S/PV.7411 (2015), at 4 (Yemen). See also Letter dated 24 April 2015 from the Permanent Representative of Qatar to the United Nations Addressed to the President of the Security Council, UN Doc. S/2015/279 (2015), at 2; Ruys and Ferro, supra note 36, at 73.

38 The United States justified its air strikes on radar facilities in Houthi-held areas in October 2016 by the fact that it had been requested by President Hadi and not Art. 51 of the UN Charter. See Letter dated 15 October 2016 from the Permanent Representative of the United States of America to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/869 (2016). See also Ruys and Ferro, supra note 36, at 71–2.

39 Letter dated 14 September 2016 from the Permanent Representative of Saudi Arabia to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/786 (2016).

40 E.g., Letter dated 2 July 1996 from the Minister for Foreign Affairs of Turkey addressed to the Secretary-General and to the President of the Security Council, UN Doc. S/1996/479 (1996); Letter dated 3 January 1997 from the Minister for Foreign Affairs of Turkey addressed to the Secretary-General and to the President of the Security Council, UN Doc. S/1997/7 (1997); Deeks, supra note 2, at 487; Jackson, supra note 23, at 183.

41 See, e.g., identical letters dated 27 June from the Charge d’Affaires a.i. of the Permament Mission of Turkey to the United Nations addressed to the Secretary-General and to the President of the Security Council, UN Doc. S/1996/479, Ann. (1996), at 2–3; Identical letters dated 1997 from the Permanent Mission of Turkey to the United Nations addressed to the Secretary-General and to the President of the Security Council, UN Doc. S/1997/7, Ann. (1997); see also Deeks, supra note 2, at 487; Jackson, supra note 23, at 183.

42 UN Doc. S/PV.7989 (2015), at 5 [Turkey]; Traynor, I., ‘Upsurge in Kurdish Attacks Raises Pressure on Turkish Prime Minister to Order Iraq Invasion’, Guardian, 9 October 2017, available at www.theguardian.com/world/2007/oct/09/turkey.iraq1Google Scholar; Jackson, supra note 23, at 185.

43 Gray, supra note 25, at 138–9.

44 See, e.g., Letter dated 25 May 1993 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the Secretary-General, UN Doc. S/25843 (1993); Letter dated 9 November 1994 from the Charge d’Affaires i.a. of the Islamic Republic of Iran to the United Nations addressed to the Secretary General, UN Doc. S/1994/1273 (1994); Letter dated 29 July 1996 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the Secretary-General, UN Doc. S/1996/602 (1996); Letter dated 13 March 2000 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the Secretary-General, UN Doc. S/2000/216, Ann. (2000); Letter dated 22 March 2001 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the Secretary-General, UN Doc. S/2001/271, Ann. (2001); Ruys, supra note 2, at 432.

45 Letter dated 29 July 1996 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the Secretary-General, UN Doc. S/1996/602 (1996); Ruys, supra note 2, at 432.

46 Letter dated 23 September 2014 from the Permanent Representative of the United States of America to the United Nations addressed to the Secretary-General, UN Doc. S/2014/695 (2014). See also Letter dated 25 June 2014 from the Permanent Representative of Iraq to the United Nations addressed to the Secretary-General, UN Doc. S/2014/440, Ann. (2014).

47 Letter dated 23 September 2014 from the Permanent Representative of the United States of America to the United Nations addressed to the Secretary-General, UN Doc. S/2014/695 (2014).

48 Letter dated 15 October 2015 from the Permanent Representative of the Russian Federation to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/792 (2015) 2; Rohani, H., ‘La lutte contre le terrorisme doit être la base de tout en Syrie’, Le Monde, 29 January 2016, available at www.lemonde.fr/international/article/2016/01/29/hassan-rohani-la-lutte-contre-le-terrorisme-doit-etre-la-base-de-tout-en-syrie_4855748_3210.htmlGoogle Scholar.

49 Corten, supra note 2, at 779.

50 See B. Ki-Moon, Remarks at the Climate Summit Press Conference (including comments on Syria), 23 September 2014, available at www.un.org/sg/en/content/sg/speeches/2014-09-23/remarks-climate-summit-press-conference-including-comments-syria; Hakimi, supra note 2, at 27.

51 Middle Eastern states that have joined the coalition included at an early stage Bahrain, Jordan, Saudi Arabia, the United Arab Emirates, and Qatar. See Reuters staff, ‘Qatar, a Partner in US Airstrikes, says Syrian Regime Main Problem’, Reuters, 24 September 2014, available at www.reuters.com/article/us-un-assembly-qatar/qatar-a-partner-in-u-s-airstrikes-says-syrian-regime-main-problem-idUSKCN0HJ24D20140924.

52 Letter dated 24 July 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/563 (2015).

53 Letter dated 9 September 2015 from the Permanent Representative of Australia to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/693 (2015), at 1; Letter dated 31 March 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Canada to the United Nations addressed to the President of the Security Council UN Doc. S/2015/221 (2015).

54 Identical letters dated 20 January 2018 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2018/53 (2018), at 1.

55 Ibid.

56 Identical letters dated 8 September 2015 from the Permanent Representative of France to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/745 (2015); Letter dated 24 July 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/563 (2015).

57 Letter dated 7 September 2015 from the Permanent Representative of the United Kingdom of Great Britain and Northern Ireland to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/688 (2015).

58 Ibid.; Letter dated 3 December 2015 from the Permanent Representative of the United Kingdom of Great Britain and Northern Ireland to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/928 (2015).

59 Brunnée and Toope (Self-Defence), supra note 2, at 271.

60 Letter dated 10 December 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Germany to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/946 (2017); Letter dated 11 January 2016 from the Permanent Representative of Denmark to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/34 (2016); Letter dated 3 June 2016 from the Permanent Representative of Norway to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/513 (2016); Letter dated 7 June 2016 from the Permanent Representative of Belgium to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/523 (2016).

61 See UN Doc. S/2016/523 (2016) (Belgium); UN Doc. S/2015/946 (2015) (Germany); Brunnée and Toope (Self-Defence), supra note 2, at 271.

62 1969 Vienna Convention on the Law of Treaties, 1155 UNTS 331.

63 ILC Report of the work of the sixty-eighth session, UN Doc. A/71/10 (2016), Ch. VI, Conclusion 7(1).

64 Ibid., Ch. VI, Conclusion 9(2).

65 ILC Report, supra note 63, Ch. VI, Commentary on Conclusion 9, paras. 10)–11.

66 Ibid., Ch. V, Conclusion 9(1).

67 Ibid., Ch. VI, Conclusion 10(2) and Commentary to Conclusion 10, para. 19 ff.

68 See also ibid., Ch. V, Commentary to Conclusion 10(1), para. 7.

69 Letter dated 7 October 2001 from the Chargé d’Affaires a.i. of the Permanent Mission of the United Kingdom of Great Britain and Northern Ireland to the United Nations addressed to the President of the Security Council, UN Doc. S/2001/947 (2001). See also Gray, supra note 25, at 115.

70 See European Council, Conclusions and Plan of Action of the Extraordinary European Council Meeting on 21 September 2001, available at www.consilium.europa.eu/media/20972/140en.pdf.

71 See Statement by the North Atlantic Council, NATO Press Release (2001), at 124, available at www.nato.int/docu/pr/2001/p01-124e.htm. See also Hakimi, supra note 2, at 9.

72 See OAS, Convocation of the Twenty-Third Meeting of Consultation of Ministers of Foreign Affairs, OEA/Ser.G.CP/Res. 796 (1293/01) (2001).

73 For example, the statement of the European Council, supra note 70, referred to UN Doc. S/RES1368 (2001). See also the Consequences of the Construction of a Wall decision, supra note 5, Declaration of Judge Buergenthal, para. 6 and Separate Opinion of Judge Kooijmans, para. 35; Tams, supra note 2, at 377; Tsagourias, supra note 2, at 806; Bethlehem, supra note 2, at 5. However, see Tladi, supra note 2, at 575 who cautions against reading too much into the general, preambular references to the right to self-defence in these Resolutions.

74 Parliamentary Assembly of the Council of Europe Recommendation, ‘The Situation in Georgia and Its Consequences for the Stability of the Caucasus Region’, Recommendation 1580 (2002), para. 5, available at www.assembly.coe.int/nw/xml/XRef/Xref-XML2HTML-en.asp?fileid=17043&lang=en; Hakimi, supra note 2, at 14; Gray, supra note 25, at 139.

75 For statements, see inter alia UN Doc. S/PV. 4836 (2003), at 3 (Syria), 8 (Pakistan, Spain, China), 9 (United Kingdom, Russia, Germany, France), 10 (Bulgaria, Mexico, Chile), 13 (United States), and 14 (League of Arab states). See also Ruys, supra note 2, at 447–8; Jackson, supra note 23, at 185.

76 UN Doc. S/PV.5498 (2016), at 3 (UNSG); Jackson, supra note 23, at 185; and Ruys, supra note 2, at 449 ff.

77 United States State Department, Daily Press Briefings of 28 March 1991, 31 March 1995, 17 April 1995, 7 July 1995, 5 September 1996, 6 November 1996, and 11 February 1998, cited in Ruys, supra note 2, at 431. See also United Kingdom statements, cited in (1995) 66 British Yearbook of International Law, at 725, and (1998) 69 British Yearbook of International Law, at 586.

78 EU Presidency Statement on the Military Action Undertaken by Turkey in Iraqi Territory, 25 February 2008, available at http://www.eu2008.si/en/News_and_Documents/CFSP_Statements/February/0225MZZturkey.html.

79 Letter dated 24 September 1996 from the Permanent Observer for the League of Arab states to the United Nations Addressed to the Secretary-General, UN Doc. S/1996/796, Ann. 1 (1996); On behalf of the Non-Aligned Movement, see the Letter dated 6 June 2000 from the Permanent Representative of South Africa to the United Nations addressed to the Secretary-General, UN Doc. A/54/917-S/2000/580 (2000), para. 137.

80 See, e.g., M. Karouney, ‘Iraq Condemns Turkish Incursion’, Reuters, 26 February 2008, available at uk.reuters.com/article/uk-turkey-iraq/iraq-condemns-turkish-incursion-idUKL2691363520080226. See also Hakimi, supra note 2, at 13.

81 United States State Department, Daily Press Briefings, 30 July 1996 and 18 September 199, cited in Ruys, supra note 2, at 432.

82 See also Ruys, supra note 2, at 432.

83 Ruys and Ferro, supra note 36, at 76.

84 Letter dated 12 February 2013 from the Permanent Representative of the Islamic Republic of Iran to the United Nations addressed to the President of the Security Council, UN Doc. S/2013/88 (2013), para. 4 ff.

85 Letter dated 14 September 2016 from the Permanent Representative of Saudi Arabia to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/786 (2016), para. 4 ff; Final Report of the Panel of Experts on Yemen, UN Doc. S/2017/81 (2017), paras. 61–2; AFP, ‘Houthis Sign Huge Finance Deal with Iran’, The New Arab, 12 March 2015, available at www.alaraby.co.uk/english/politics/2015/3/12/houthis-sign-huge-finance-deal-with-iran; Ruys and Ferro, supra note 36, at 75.

86 E.g., identical letters dated 26 September 2014 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. A/69/411–S/2014/705 (2015), para. 6; Identical letters dated 25 May 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. A/69/912–S/2015/371 (2015), at 1–2; identical letters dated 29 June 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. A/69/969-S/2015/487 (2015), at 1–2. See also Goodman, R., ‘Is the United States Already in an “International Armed Conflict” with Syria?’, Just Security, 11 October 2016, available at www.justsecurity.org/33477/united-states-international-armed-conflict-syria/Google Scholar; Gray, supra note 25, at 172.

87 Identical letters dated 17 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary General and the President of the Security Council, UN Doc. S/2015/719 (2015).

88 See inter alia identical letters dated 2 June 2015 from the Permanent Representative of Jordan to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/A/69/923–S/2015/403 (2015); identical letters dated 16 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/718 (2015); identical letters dated 17 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/719 (2015).

89 Identical letters dated 16 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/718 (2015); identical letters dated 17 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/719 (2015). See also Tsagourias, supra note 2, at 803.

90 Identical letters dated 29 December 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. A/70/673- S/2015/1048 (2016), para. 4; see also Corten, supra note 2, at 787.

91 Russia described the air strikes against IS in Syria without the consent of the Assad government as an act of aggression. See A. Anishchuk and J. Irish, ‘Russia Says Air Strikes in Syria Would Be an Act of Aggression Without UN Vote’, Reuters, 11 September 2014, available at uk.reuters.com/article/uk-russia-u-s-syria-airstrikes/russia-says-air-strikes-in-syria-would-be-act-of-aggression-without-u-n-vote-idUKKBN0H61BF20140911; I. Black and D. Roberts, ‘Isis Air Strikes: Obama's Plan Condemned by Syria, Russia and Iran’, Guardian, 12 September 2014, available at www.theguardian.com/world/2014/sep/11/assad-moscow-tehran-condemn-obama-isis-air-strike-plan; Corten, supra note 2, at 788–9; Starski, supra note 2, at 487.

92 See Ministry of Foreign Affairs of the Peoples’ Republic of China, Foreign Ministry Spokesperson Hua Chunying's Regular Press Conference, 23 September 2014, transcript available at www.fmprc.gov.cn/mfa_eng/xwfw_665399/s2510_665401/t1194096.shtml.

93 P. Stewart and T. Perry, ‘US and Arab Allies Launch First Strikes on Militants in Syria’, Reuters, 23 September 2014, available at www.reuters.com/article/us-syria-crisis-usa-strikes/u-s-and-arab-allies-launch-first-strikes-on-militants-in-syria-idUSKCN0HI03A20140923.

94 Brunnee and Toope (Self-Defence), supra note 2, at 270. See also Flasch, O., ‘The Legality of the Air Strikes Against ISIL in Syria: New Insights on the Extraterritorial Use of Force against Non-State Actors’, (2016) 3 Journal of the Use of Force and International Law, at 60CrossRefGoogle Scholar.

95 However, see Starski, supra note 2, at 489, according to whom the normative value of the prohibition of the use of force in international law requires explicit approval as opposed to tacit acquiescence.

96 See Global Coalition against Daesh, ‘Guiding Principles from the Global Coalition to Defeat Daesh’, 3 February 2018, available at theglobalcoalition.org/en/guiding-principles-global-coalition-defeat-daesh/.

97 The 17th Summit of Heads of State and Government of the Non-Aligned Movement, Final Document, para. 25.2, NAM 2016/CoB/DOC.1. Corr.1 (2017).

98 Flasch, supra note 94, at 64.

99 As is suggested by Brunnée and Toope (Self-Defence), supra note 2, at 275.

100 UN Doc. S/PV.8181 (2018), at 11 (Syria); UN Doc. S/PV.8195 (2018), at 20 (Syria).

101 DPA, ‘Merkel verurteilt erstmals türkische Syrien-Offensive’, Handelsblatt, 21 March 2018, available at www.handelsblatt.com/politik/deutschland/inakzeptabel-was-in-afrin-geschieht-merkel-verurteilt-erstmalstuerkische-syrien-offensive/21099162.html.

102 Ibid.

103 European Parliament, European Parliament Resolution on the Situation in Syria, 2018/2626 (RSP) (2018), para. F. See also the reaction of Iran, whose criticism concerned the political ramifications of the intervention. K. Sulaivany, ‘Iran Latest to Condemn Turkish Military Campaign Against Kurds in Afrin’, Kurdistan 24, 21 January 2018, available at www.kurdistan24.net/en/news/5ed63e9f-1483-4267-95d9-ccb90acd5e27.

104 See also P.A. Nollkaemper, ‘Nader Advies Geweldgebruik Tegen ISIL in Syrie’, 23 June 2015, para. 14, available at www.internationaal-recht.nl/documents/20531/0/Kabinetsreactie-en-Nader-Advies-Extern-Volkenrechtelijke-advisseur-geweldgebruik-tegen-ISIS-in-Syri-.pdf/b8001b7f-9629-1010-36f0-9d31e363163c?version=1.0. However, see Brunnee and Toope (Self-Defence), supra note 2, at 266. They note that it has mainly been invoked by powerful Western states referring predominantly to their own practice.

105 See also ILC Report, supra note 63, Ch. V, Conclusion 8(1) and Commentary to Conclusion 9(1), para. 5.

106 See ibid., Ch. V, Commentary on Conclusion 8(1), para. 4, that attaches significant weight to the behaviour of particularly involved states.

107 See also Hakimi, supra note 2, at 9; C. Kress, ‘The Fine Line Between Collective Self-Defence and Intervention by Invitation: Reflections on the Use of Force against IS in Syria’, Just Security, 17 February 2015, available at www.justsecurity.org/20118/claus-kreb-force-isil-syria/.

108 In the Nicaragua decision, supra note 4, para. 85 ff, as well as the Democratic Republic of the Congo decision, supra note 5, para. 72 ff, the lack of evidence of [state involvement] in the alleged armed attacks was one important factor influencing the ICJ’s decision. See also Ruys, supra note 2, at 494; Charney, supra note 2, at 836 ff; Franck, supra note 2.

109 Flasch, supra note 94, at 57.

110 Art. 8 ASR, supra note 17, which represents the customary standard, determines that ‘[c]onduct of a person or group of persons shall be considered an act of a state under international law if the person or group of persons is in fact acting on the instructions of, or under the direction or control of, that state in carrying out the conduct’. See also Case Concerning Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v. Serbia and Montenegro), Merits, Judgment of 26 February 2007, [2007] ICJ Rep. 43, paras. 406, 659; Tams, supra note 2, at 385; Tsagourias, supra note 2, at 805; Jackson, supra note 23, at 181; Lanovoy, supra note 2, at 566.

111 Brunnee and Toope (Self-Defence), supra note 2, at 273.

112 Some authors nonetheless insist that the mere provision of weapons or financial support would not amount to ‘substantial involvement’. They propose involvement comparable to ‘overall control’, as articulated in Prosecutor v. Tadic, Judgement, Case No. IT-94-1-A, Appeals Chamber, 15 July 1999, para. 137. See Ruys and Ferro, supra note 36, at 75. See also Tsagourias, supra note 2, at 806, 818; Randelzhofer and Nolte, supra note 2, at 1416. However, see Corten, supra note 2, at 794 ff, who is highly critical of any expansive interpretation of an armed attack.

113 Tsgagourias, supra note 2, at 806 and 816.

114 Tams, supra note 2, at 384–5; Brunee and Toope (Use of Force), supra note 2, at 795.

115 Tsgagourias, supra note 2, at 806 and 818; Lanovoy, supra note 2, at 582.

116 Some authors prefer to describe this combination of knowledge (at the time the non-state actor was present on its territory) and the causality between such presence and the armed attack perpetrated by the non-state actor as complicity. See notably Lanovo, supra note 2, at 582 ff. Contra Plakokefalos, I., ‘The Use of Force by Non-State Actors and the Limits of Attribution of Conduct: A Reply to Vladyslav Lanovoy’, (2017) 28 European Journal of International Law, at 587–93CrossRefGoogle Scholar.

117 See Brunee and Toope (Self-Defence), supra note 2, at 273–4; Starski, supra note 2, at 498.

118 Letter dated 23 September 2014 from the Permanent Representative of the United States of America to the United Nations addressed to the Secretary-General, UN Doc. S/2014/695 (2014).

119 Letter dated 9 September 2015 from the Permanent Representative of Australia to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/693 (2015).

120 Letter dated 31 March 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Canada to the United Nations addressed to the President of the Security Council UN Doc. S/2015/221, 31 March 2015; Letter dated 24 July 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/563 (2015).

121 Trapp, K., ‘Back to Basics: Necessity, Proportionality, and the Right of Self-Defence Against Non-State Terrorist Actors’, (2007) 56 International and Comparative Law Quarterly, at 146.CrossRefGoogle Scholar

122 Ruys and Ferro, supra note 36, at 93–4.

123 See Ruys, supra note 2, at 434–5.

124 Bethlehem, supra note 2, at 7; Trapp, supra note 121, at 147. See also Charney, supra note 2, at 836 ff.

125 See also Deeks, supra note 2, at 519–20, 540, 543; Hakimi, supra note 2, at 10–11.

126 See Case Concerning Oil Platforms (Islamic Republic of Iran v. United States of America), Judgment of 6 November 2003, [2003] ICJ Rep. 161, para. 74. The ICJ was not convinced, in light of the evidence, that the actual platforms targeted by the United States constituted a staging base for launching small-scale attacks on neutral, commercial shipping vessels; Ruys, supra note 2, at 109–10.

127 E.g., Brunnée and Toope (Use of Force), supra note 2, at 895–6. See also Bethlehem, supra note 2, at 7.

128 Ruys, supra note 2, at 108 and 111 ff.

129 Ruys, ibid.; Randelzhofer and Nolte, supra note 2, at 1427; Trapp, supra note 121, at 146.

130 See also Final Report of the Panel of Experts on Yemen, supra note 85, paras. 119, 126 ff.

131 See also Institut de Droit International, Present Problems of the Use of Armed Force in International Law, Resolution 10A, 27 October 2007, para. 10(ii), available at www.idi-iil.org/app/uploads/2017/06/2007_san_02_en.pdf; Brunnee and Toope (Self-Defence), supra note 2, at 274.

132 See inter alia Report of the Secretary-General on the Implementation of Security Council Resolutions 2139 (2014) and 2165 (2014), UN Doc. S/2014/756 (2014), para. 59; Report of the Secretary-General on the Implementation of Security Council Resolution 2139 (2014), 2165 (2014) and 2191 (2014), UN Doc. S/2015/2016 (2015), para. 13; Report of the Secretary-General on the implementation of Security Council Resolutions 2139 (2014), 2165 (2014), 2191 (2014), 2258 (2015) and 2332 (2016), UN Doc. S/2017/794 (2017), para. 6. See also Corten, supra note 2, at 792.

133 See Letter dated 7 June 2016 from the Permanent Representative of Belgium to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/523 (2016); Letter dated 10 December 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Germany to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/946 (2015/946). See also Brunnee and Toope (Self-Defence), supra note 2, at 272.

134 Identical letters dated 20 January 2018 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2018/53 (2018), at 1.

135 Compare also Brunnée and Toope (Self-Defence), supra note 2, at 272.

136 Tsagourias, supra note 2, at 809; Jackson, supra note 23, at 186.

137 Letter dated 10 December 2015 from the Chargé d’Affaires a.i. of the Permanent Mission of Germany to the United Nations addressed to the President of the Security Council, UN Doc. S/2015/946 (2015); Letter dated 7 June 2016 from the Permanent Representative of Belgium to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/523 (2016); Letter dated 3 June 2016 from the Permanent Representative of Norway to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/513 (2016). See also Tsagourias, supra note 2, at 811.

138 Identical letters dated 20 January 2018 from the Chargé d’Affaires a.i. of the Permanent Mission of Turkey to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2018/53 (2018), at 1.

139 UN Doc. S/RES/2249 (2015), para. 5.

140 Letter dated 11 January 2016 from the Permanent Representative of Denmark to the United Nations addressed to the President of the Security Council, UN Doc. S/2016/34 (2016).

141 Deutscher Bundestag (Antrag der Bundesregierung), Einsatz bewaffneter deutscher Streitkräfte zur Verhütung und Unterbindung terroristischer Handlungen durch die Terrororganisation IS auf Grundlage von Artikel 51 der Satzung der Vereinten Nationen in Verbindung mit Artikel 42 Absatz 7 des Vertrages über die Europäische Union sowie den Resolutionen 2170 (2014), 2199 (2015), 2249 (2015) des Sicherheitsrates der Vereinten Nationen, Drucksache 18/6866 (2015), at 3, stating: ‘The action against IS in the execution of ‘[t]he right to collective self-defence in accordance with Article 51 of the Charter of the United Nations is covered by United Nations Security Council Resolution 2249 (2015)’ (‘Das Vorgehen gegen den IS in Wahrnehmung des kollektiven Selbstverteidigungsrechts gemäß Artikel 51 der Charta der Vereinten Nationen ist von der Resolution 2249 (2015) des Sicherheitsrates der Vereinten Nationen umfasst.’) translation by author.

142 See Corten, supra note 2, at 791, who distinguishes UN Doc. S/RES/2249 (2015) from UN Doc. S/RES/1368 (2001), which in the Preamble referred to the right to self-defence.

143 Flasch, supra note 94, at 59. See also D. Akande and M. Milanovic, ‘The Constructive Ambiguity of the Security Council’s ISIS Resolution’, EJIL:Talk!, 21 November 2015, available at www.ejiltalk.org/the-constructive-ambiguity-of-the-security-councils-isis-resolution/.

144 See Corten, supra note 2, at 791.

145 However, see Corten, ibid., at 798; O’Connell, M.E., ‘Dangerous Departures’, (2013) 107 American Journal of International Law, at 380, 383Google Scholar. They question whether the evolving state practice is sufficiently widespread and accepted on this point.

146 Art. 1(c) of the AU Non-Aggression and Common Defence Pact, supra note 29, determines: ‘Aggression means the use, intentionally and knowingly, of armed force or any other hostile act by a state, a group of states, an organization of states or non-state actor(s) or by any foreign or external entity, against the sovereignty, political independence, territorial integrity and human security of the population of a state party to this Pact …’.

147 See Democratic Republic of the Congo decision, supra note 5, Separate Opinion of Judge Simma, para. 12, and Separate Opinion of Judge Kooijmans, para. 30. In their respective individual opinions in the Advisory Opinion on the Construction of a Wall in the Occupied Territories, Judges Buergenthal, Higgins, and Kooijmans underscored that the wording of Art. 51 of the UN Charter did not make the exercise of the right to self-defence dependent on an armed attack by a state. Construction of a Wall decision, supra note 5, Declaration of Judge Buergenthal, para. 6, Separate Opinion of Judge Higgins, para. 33, and Separate Opinion of Judge Kooijmans, para. 35. See also Franck, supra note 2, at 840; Hakimi, supra note 2, at 10; Tsagourias, supra note 2, at 811.

148 Trapp, supra note 121, at 146.

149 See also Tsagourias, supra note 2, at 804; Sloane, R.D., ‘In the Use and Abuse of Necessity in the Law of State Responsibility’, (2012) 106 American Journal of International Law, at 505Google Scholar.

150 See also Sloane, ibid., at 491–2.

151 See Tsagourias, supra note 2, at 804 ff, who argues that the justification for the intrusion in the territory of the (‘unable’) state where the non-state perpetrator is located stems from Art. 21 of the ASR, supra note 17, a secondary norm. This article determines that ‘[t]he wrongfulness of an act of a state is precluded if the act constitutes a lawful measure of self-defence taken in conformity with the Charter of the United Nations’.

152 See inter alia F. Paddeu, Justification and Excuse in International Law (2018), at 55–6. The ASR also contains norms with both primary and secondary characteristics.

153 Art. 25(1) of ASR, supra note 17 determines: ‘Necessity may not be invoked by a state as a ground for precluding the wrongfulness of an act not in conformity with an international obligation of that state unless the act (a) is the only way for the state to safeguard an essential interest against a grave and imminent peril; and (b) does not seriously impair an essential interest of the state or states towards which the obligation exists, or of the international community as a whole.’

154 Art. 25(1)(a), ASR, supra note 17.

155 While Art. 25 is placed in Ch. V of the ASR, supra note 17, which concerns circumstances precluding wrongfulness, it remains disputed whether necessity constitutes an excuse (that mitigates the responsibility arising from a wrongful act) or a justification (that excludes the illegality of the act). See Johnstone, I., ‘The Plea of Necessity in International Legal Discourse: Humanitarian Intervention and Counter-Terrorism’, (2005) 43 Columbia Journal of Translational Law, at 353–4Google Scholar; Sloane, supra note 149, at 484; Paddeu, supra note 152, at 414 ff.

156 The ASR also does not apply directly to conduct which is regulated by specialized regimes such as the jus ad bellum. Art. 55 ASR, supra note 17, determines that these articles ‘do not apply where and to the extent that the conditions for the existence of an internationally wrongful act or the content or implementation of the international responsibility of a state are governed by special rules of international law’. See also ILC Commentary to Art. 25 ASR, supra note 17, para. 21; Sloane, supra note 149, at 494.

157 ILC Commentary to Art. 25 ASR, supra note 17, para. 14; Johnstone, supra note 155, at 356.

158 See also Starski, supra note 2, at 491.

159 ILC Commentary to Art. 25 ASR, supra note 17, paras. 15–16; Johnstone, supra note 155, at 37; Ruys, supra note 2, at 378–9.

160 The Caroline incident of 1837 is often cited as a famous example of necessity in self-defence. See British and Foreign state Papers: 1840–1841, Vol. 29 (1857), 1129; ILC Commentary to Art. 25 ASR, supra note 17, para. 5; Sloane, supra note 149, at 457. See also Johnstone, supra note 155, at 368.

161 E.g., Brunnée and Toope (Use of Force), supra note 2, at 895–6; see also Bethlehem, supra note 2, at 7.

162 See, e.g., identical letters dated 16 September 2015 from the Permanent Representative of the Syrian Arab Republic to the United Nations addressed to the Secretary-General and the President of the Security Council, UN Doc. S/2015/718 (2015); Tsagourias, supra note 2, at 809; Zamani and Nikouei, supra note 34, at 19.

163 Kress, supra note 107; Tsagourias, supra note 2, at 809; Nollkaemper, supra note 104, para. 5.

164 See, e.g., UN Human Rights Council, First Report of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN Doc. A/HRC/S-27/2/Add.1 (2011), para. 51 ff; and Seventh Report of the Independent International Commission of Inquiry on the Syrian Arab Republic, UN Doc. A/HRC/25/65 (2014), para. 21 ff.

165 Brunnée and Toope (Self-Defence), supra note 2, at 280–1; see also von Bernstorff, J., ‘Drone Strikes, Terrorism and the Zombie: On the Construction of an Administrative Law of Transnational Executions’, (2016) 5 European Society of International Law (ESIL) Reflections, available at www.esil-sedi.eu/node/1368Google Scholar.