¹ Chemical Weapon Use by Syrian Regime: UK Government Legal Position (29 August 2013) <https://www.gov.uk/government/publications/chemical-weapon-use-by-syrian-regime-uk-government-legal-position/chemical-weapon-use-by-syrian-regime-uk-government-legal-position-html-version> (hereinafter ‘UK Legal Opinion’). The full opinion is appended at the end of this article.

² See section IV.

³ See Stahn, C, ‘Syria and the Semantics of Intervention, Aggression and Punishment: On “Red Lines” and “Blurred Lines”’ (2013) 11 JICJ 955Google Scholar and S Darcy, ‘Military force against Syria would be a reprisal rather than humanitarian intervention, but that doesn't make it any more lawful’ (EJIL Talk!, 1 September 2013) <http://www.ejiltalk.org/author/sdarcy/>.

⁴ UK Legal Opinion (n 1) para 2. Humanitarian intervention can be described as the use or threat of force by one or more States or an international organization to protect individuals in the target State from grave suffering or deprivation of fundamental human rights. See Murphy, SD, Humanitarian Intervention: The United Nations in an Evolving World Order (University of Pennsylvania Press 1996) 11–12Google Scholar.

⁵ For more on this see section IV of this article.

⁶ See section III.

⁷ As Finnemore and Sikkink point out: ‘The characteristic mechanism of … norm emergence is persuasion by norm entrepreneurs. Norm entrepreneurs attempt to convince a critical mass of States (norm leaders) to embrace new norms.’ M Finnemore and Sikkink, K, ‘International Norm Dynamics and Political Change’ (1998) 52 IntlOrg 894, 895Google Scholar. See also section IV.

⁸ UK Legal Opinion (n 1) para 1.

⁹ See ‘Attorney General's Advice on the Iraq War: Resolution 1441’ (2005) 54 ICLQ 767.

¹⁰ UK Legal Opinion (n 1) para 2.

¹¹ This concept was first introduced in Report of the International Commission on Intervention and State Sovereignty, The Responsibility to Protect (December 2001) <http://responsibilitytoprotect.org/ICISS%20Report.pdf>.

¹² See High-Level Panel on Threats, Challenges, and Change, A more secure world: our shared responsibility, 2 December 2004, UN Doc A/59/565, para 203. It has also been described as ‘soft law’. See J Welsh and M Banda, ‘International Law and the Responsibility to Protect: Clarifying or Expanding States’ Responsibilities?’ (2010) 2 Global Responsibility to Protect 213, 230.

¹³ See, recently, D Bethlehem, ‘Stepping Back a Moment – The Legal Basis in Favour of a Principle of Humanitarian Intervention’ (EJIL Talk!, 12 September 2013) <http://www.ejiltalk.org/stepping-back-a-moment-the-legal-basis-in-favour-of-a-principle-of-humanitarian-intervention/>.

¹⁴ See Green, JA, The International Court of Justice and Self-Defence in International Law (Hart Publishing 2009) 63–110Google Scholar.

¹⁵ The Legal Opinion came to the conclusion that ‘all these conditions would clearly be met in this case’. See UK Legal Opinion (n 1) para 5. The UK has proffered more detailed conditions previously, albeit in the abstract. See, for example, P Reynolds, ‘Blair's “international community” doctrine’ (BBC News, 6 March 2004) <http://news.bbc.co.uk/1/hi/uk_politics/3539125.stm>.

¹⁶ UK Legal Opinion, ibid, para 4(i).

¹⁷ See United Nations Mission to Investigate Allegations of the Use of Chemical Weapons in the Syria Arab Republic, Report on the Alleged Use of Chemical Weapons in the Ghouta Area of Damascus on 21 August 2013 (13 September 2013) <http://www.un.org/disarmament/content/slideshow/Secretary_General_Report_of_CW_Investigation.pdf>.

¹⁸ UK Legal Opinion (n 1) para 4(1)(i).

¹⁹ ibid, para 4(ii).

²⁰ See section IV for more on the reaction of other States to the possible use of force.

²¹ UK Legal Opinion (n 1) para 4(1)(ii).

²² ibid, para 4(iii).

²³ ibid, para 4(1)(iii).

²⁴ ibid. It has, however, been questioned by Stahn whether the ‘doctrine of “humanitarian intervention” offers a proper fit for the motives of intervention’. This was because unlike interventions on other occasions, intervention here ‘was guided by other purposes, namely (i) shifting the military balance between the Assad regime and opposition forces and (ii) sanctioning an unlawful means of combat, that is, use of chemical weapons.’ See C Stahn, ‘Between Law-breaking and Law-making: Syria, Humanitarian Intervention and “What the Law Ought to Be”’ (2014) 19 JC&SL 25, 30.

²⁵ UK Legal Opinion, ibid, paras 2 and 4.

²⁶ ibid, para 4(1)(i).

²⁷ This can also be found in the US's justifications for the prospective use of force in this context. See section IV. On the concept of ‘anticipatory humanitarian intervention’ see J Charney, ‘Anticipatory Humanitarian Intervention in Kosovo’ (1999) 93 AJIL 834.

²⁸ UK Legal Opinion (n 1) para 4(1)(iii).

²⁹ ibid, para 4.

³⁰ ibid, para 4(1)(iii) (emphasis added).

³¹ For a good account of these various views see Burke, C, An Equitable Framework for Humanitarian Intervention (Hart Publishing 2013) 6–89Google Scholar.

³² Stahn (n 24) 32.

³³ O Corten, The Law Against War: The Prohibition on the Use of Force in Contemporary International Law (Hart Publishing 2010) 4–27.

³⁴ UK Foreign Office Policy Document No 148. See (1986) 57 BYBIL 614, 619.

³⁵ Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1984] ICJ Rep 14, para 34.

³⁶ Corten (n 33) 16.

³⁷ Nicaragua case (n 35) para 176.

³⁸ See Chapter XVIII of the UN Charter (1945). Given that virtually every State is subject to the prohibition in Article 2(4), any agreement to amend its scope would arguably also have a knock-on effect for the customary contours or existence of the norm, in the absence, that is, of any statement limiting the applicability of the modifying agreement.

³⁹ The International Law Commission expressed the view that ‘the law of the Charter concerning the prohibition of the use of force in itself constitutes a conspicuous example of a rule in international law having the character of jus cogens’. See (1996-II) UNYBILC 247. It is also significant that the International Court of Justice also noted in the Nicaragua case that the prohibition ‘is frequently referred to in statements by state representatives as being … a fundamental or cardinal principle’. See Nicaragua case (n 35) para 190 (emphasis added). Although, see, in general, Green, JA, ‘Questioning the Peremptory Status of the Prohibition of the Use of Force’ (2011) 32 MichJIntlL 215Google Scholar.

⁴⁰ See Chapter VII of the UN Charter. There is no express exception to Article 2(4) of humanitarian intervention contained within the Charter, which might seem surprising given that the UN Charter was drafted during the horrors of the Holocaust.

⁴¹ While the norm prohibiting the threat or use of force is widely held as being jus cogens, an agreement may emerge amongst the State parties to the Charter regarding its (re)interpretation thus subjecting the norm to of a process of modification. Art 53 of the Vienna Convention on the Law of Treaties declares that ‘a peremptory norm of general international law is a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character’. There does not, however, seem to be anything preventing the ‘international community of States as a whole’ from simply agreeing to cease the applicability of the prohibition of the use of force without necessarily replacing it with a subsequent norm of a jus cogens nature.

⁴² See arts 31(2)(a) and (b) and 31(3)(a) and (b) of the VCLT. The VCLT is a treaty that has been ratified by 114 States with others recognizing it, or elements of it, as a restatement of customary international law.

⁴³ Stahn (n 24) 34.

⁴⁴ The UK was somewhat equivocal in its 1986 policy document in stating that the UN Charter and the corpus of modern international law does ‘not seem specifically to incorporate such a right’ (emphasis added).

⁴⁵ Art 31(4) of the VCLT.

⁴⁶ See Randelzhofer, A, ‘Article 2(4)’ in Simma, B (ed), The Charter of the United Nations: A Commentary (2nd edn, Oxford University Press 2002) 112 at paras 37–39Google Scholar. Michael Akehurst stated that ‘the travaux préparatoires indicated that the reference to territorial integrity, political independence, and the purposes of the United Nations was added to Article 2(4), not in order to limit the prohibition on the use of force, but in a clumsy attempt to strengthen it’. See M Akehurst, ‘Humanitarian Intervention’ in H Bull (ed), Intervention in World Politics (Clarendon Press 1986) 95. See also Brownlie, I, The Rule of Law in International Affairs (Martinus Nijhoff 1998) 198Google Scholar.

⁴⁷ See, for example, Bowett, D, Self-Defence in International Law (Manchester University Press 1958) 152Google Scholar.

⁴⁸ There was also an implicit rejection of the argument by the International Court of Justice after it had been put forward by the UK to defend its incursion into Albanian waters in the Corfu Channel case. See Corfu Channel Case (United Kingdom v Albania) [1949] ICJ Rep 4, at 35. It was not accepted by many States following Israel's reliance upon it to justify its incursion into Ugandan territory in 1979 to rescue Israeli nationals that had been taken hostage on an aircraft by a group of Palestinians. See Shaw, M, International Law (6th edn, Cambridge University Press 2008) 1144CrossRefGoogle Scholar.

⁴⁹ In the Legality of Use of Force case of 1999 Belgium made a similar argument in the ICJ. It argued for the legality of NATO's intervention in Kosovo on the basis that it ‘never questioned the political independence and the territorial integrity of the Federal Republic of Yugoslavia’ and was as such an ‘armed humanitarian intervention, compatible with Article 2, paragraph 4, of the Charter, which covers only intervention against the territorial integrity or political independence of a State’. However, Belgium was relatively isolated in making this argument which was not one that the Court had the opportunity to express its opinion on as it did not ultimately hear the case for jurisdictional reasons, most notably Serbia and Montenegro's lack of locus standi before the Court. See Legality of Use of Force (Serbia and Montenegro v Belgium), Oral Proceedings, Public sitting, 10 May 1999, 12.

⁵⁰ See, for example, Teson, FR, Humanitarian Intervention: An Inquiry into Law and Morality (2nd edn, Transnational Publishers 1997) 151Google Scholar.

⁵¹ Art 55(c), UN Charter (1945).

⁵² Art 56, ibid.

⁵³ Henderson, C, The Persistent Advocate and the Use of Force: The Impact of the United States upon the Jus ad Bellum in the Post-Cold War Era (Ashgate 2010) 119Google Scholar.

⁵⁴ See, generally, M Reisman, ‘Coercion and Self-Determination’ (1984) 78 AJIL 642.

⁵⁵ ibid.

⁵⁶ Declaration on Principles of International Law Concerning Friendly Relations and Co-operation Among States in Accordance with the Charter of the United Nations, 24 October 1970, GA Res 2625 (XXV) (1970).

⁵⁷ In similar terms, the Definition of Aggression provides that ‘[n]o consideration of whatever nature, whether political, economic, military or otherwise, may serve as a justification for aggression’. Definition of Aggression, 14 December 1974, GA Res 3314 (XXIX) (1974).

⁵⁸ 2005 World Summit Outcome document, UNGA Res A/60/L.1 (15 September 2005), paras 138–139.

⁵⁹ Report of the UN Secretary-General, Implementing the Responsibility to Protect, UN Doc A/63/677, 12 January 2009, para 3 (emphasis added).

⁶⁰ Art 4(h), Constitutive Act of the African Union (2000).

⁶¹ Stahn (n 24) 38.

⁶² See, for example, Declaration on Friendly Relations (n 56); Definition of Aggression (n 57); 2005 World Summit Outcome document (n 58).

⁶³ See C Henderson, ‘The centrality of the United Nations Security Council in the legal regime governing the use of force’ in ND White and C Henderson (eds), Research Handbook on International Conflict and Security Law: Jus ad Bellum, Jus in Bello, and Jus post Bellum (Edward Elgar 2013) 120, 137.

⁶⁴ See Bethlehem (n 13).

⁶⁵ Art 31(3)(b) of the VCLT (emphasis added).

⁶⁶ See, for example, Corten (n 33) 29.

⁶⁷ See (1971) UNYB 146; Keesing's Record of World Events (1979) 29613; Keesing's Record of World Events (1979) 29669–73.

⁶⁸ ibid.

⁶⁹ See, for example, UNGA Resolution 34/22 (1979). See also NJ Wheeler, Saving Strangers. Humanitarian Intervention in International Society (Oxford University Press 2000) 55–136.

⁷⁰ See UK Materials on International Law, (1992) 63 BYIL 824; UNSC Verbatim Record (24 March 1999) UN Doc S/PV. 3988.

⁷¹ Henderson (n 53) 100–5.

⁷² ibid, 103–4.

⁷³ ibid.

⁷⁴ See, for example, UNSC Verbatim Record (24 March 1999) UN Doc S/PV. 3988, Russia (at 2) and China (at 12).

⁷⁵ Group of 77 South Summit, ‘Declaration of the South Summit’ (Havana, Cuba, 10–14 April 2000), para 54 (emphasis added).

⁷⁶ See A Aust, Statement before the House of Commons Foreign Affairs Select Committee, 2 December 1992, in (1992) 63 BYBIL 827–8.

⁷⁷ For example the UK claimed in connection with the intervention in Kosovo that ‘on the grounds of overwhelming humanitarian necessity, military intervention is legally justifiable’. UNSC Verbatim Record (24 March 1999) UN Doc S/PV. 3988, UK (at 12). See also US (at 4), Slovenia (at 6), Gambia (at 7), Netherlands (at 8), France (at 9), Malaysia (at 10), Argentina (at 11) and Slovenia (at 19). A possible way by which unilateral humanitarian interventions might be justified is by the invocation of necessity as a circumstance precluding wrongfulness. Art 25 of the International Law Commission's Draft Articles on State Responsibility (2001) provides that a state may be exempted from international responsibility following a violation of international law if the violation ‘[i]s the only way for the state to safeguard an essential interest against a grave and imminent peril’. The problem with invoking necessity in this context, however, is that it cannot be so invoked if the action would ‘seriously impair an essential interest of the state or states towards which the obligation exists, or of the international community as a whole’. It is difficult to see how the territorial integrity or sovereignty of the State concerned would not be deemed such an essential interest. Furthermore, Article 26 is clear that necessity cannot preclude ‘the wrongfulness of any act of a state which is not in conformity with an obligation arising under a peremptory norm of general international law’. While the debate is somewhat open as to whether it is force or that of a particularly aggressive nature which is prohibited as a jus cogens norm, the pronouncements of the International Court of Justice in the Nicaragua case and comments by the International Law Commission would seem to suggest it may be the former. See above n 39.

⁷⁸ See, for example, Brownlie, I and Apperley, CJ, ‘Kosovo Crisis Inquiry: Memorandum on the International Law Aspects’ (2000) 49 ICLQ 878CrossRefGoogle Scholar.

⁷⁹ B Simma, ‘NATO, the UN and the Use of Force: Legal Aspects’ (1999) 10 EJIL 1, 1.

⁸⁰ Franck, TM, Recourse to Force: State Action Against Threats and Armed Attacks (Cambridge University Press 2002) 180CrossRefGoogle Scholar.

⁸¹ See Cassese, A, ‘A Follow-Up: Forcible Humanitarian Countermeasures and Opinio Necessitatis’ (1999) 10 EJIL 791, 797–8CrossRefGoogle Scholar.

⁸² See section IV.

⁸³ Bethlehem (n 13).

⁸⁴ ibid.

⁸⁵ See Report of the ICISS (n 11) sections 4 and 6.

⁸⁶ See High-Level Panel report (n 12) para 181; Report of the United Nations Secretary-General, ‘In Larger Freedom: Towards Security, Development and Human Rights for All’ (21 March 2005) UN Doc A/59/205, paras 125 and 135; 2005 World Summit Outcome document (n 58) para 139. This follows from the embedded practice of the Council in determining internal crises to be ‘threats to the peace’ and thus opening up its Chapter VII powers.

⁸⁷ UNSC Resolution 1973 (2011) in its preamble only reiterated ‘the responsibility of the Libyan authorities to protect the Libyan population’ with no reference to the responsibility of the international community or the UNSC to do so if the Libyan authorities were not able or willing to. See also Henderson, C, ‘International Measures for the Protection of Civilians in Libya and Côte d'Ivoire’ (2011) 60 ICLQ 767, 778CrossRefGoogle Scholar.

⁸⁸ While NATO's Secretary-General, Anders Fogh Rasmussen, was adamant that authorization from the UNSC was required, the UK equivocally stated the need for ‘lawful authority’ to use force in Libya. See ibid. It should be noted that in the debates in Parliament in August 2013 regarding the UK's possible involvement in a direct forcible intervention in Syria a number of MPs who spoke out in favour of intervention did so upon the basis of the emergence of R2P. See, for example, House of Commons Daily Debates (29 August 2013) cols 1430, 1443 and 1514.

⁸⁹ Report of the ICISS (n 11) para 6.13.

⁹⁰ The only possibility outside of express a priori authorization by the UNSC which has been floated to any great extent in the face of a block in the UNSC is action by regional organizations which is then subsequently approved by the UNSC ex post facto. The High-Level Panel, for example, has seemingly given some credence to this option. See High-Level Report (n 12) para 272(a). This is arguably a result of the ECOWAS interventions in Liberia in 1990 and Sierra Leone in 1998, both of which were followed by endorsement of the UNSC. See, respectively, UNSC Resolution 788 (1992), para 1, and UN Doc S/PRST/1998/5 (26 February 1998) para 5.

⁹¹ UK Legal Opinion (n 1) para 3.

⁹² See, for example, V Giret et al, ‘Réforme pénale, Syrie, pression fiscale … Hollande s'explique dans “Le Monde”’ (Le Monde, 30 September 2013) <http://www.lemonde.fr/politique/article/2013/08/30/hollande-au-monde-le-massacre-de-damas-ne-peut-ni-ne-doit-rester-impuni_3468851_823448.html>.

⁹³ Danish Ministry of Foreign Affairs, ‘General principled considerations on the legal basis for a possible military operation in Syria’ UPN Alm.del Bilag 298 (30 August 2013) <http://www.ft.dk/samling/20121/almdel/upn/bilag/298/1276299/index.htm>. See also A Henriksen and M Schack, ‘The Crisis in Syria and Humanitarian Intervention’ (2014) 1 Journal on the Use of Force and International Law 122, 127.

⁹⁴ President Obama had just a year earlier drawn a ‘red line’ in regard to the use of chemical weapons, the crossing of which was said to affect his calculus in terms of the degree of intervention that he would be willing to engage in. See M Landler, ‘Obama Threatens Force against Syria’ (New York Times, 20 August 2012) <http://www.nytimes.com/2012/08/21/world/middleeast/obama-threatens-force-against-syria.html?_r=0>.

⁹⁵ The White House, Remarks by the President in Address to the Nation on Syria (10 September 2013) <http://www.whitehouse.gov/the-press-office/2013/09/10/remarks-president-address-nation-syria>.

⁹⁶ C Savage, ‘Obama Tests Limits of Power in Syria Conflict’ (New York Times, 8 September 2013) <http://www.nytimes.com/2013/09/09/world/middleeast/obama-tests-limits-of-power-in-syrian-conflict.html?pagewanted=all&action=click&module=Search&region=searchResults&mabReward=relbias%3As&url=http://%3A%2F%2Fquery.nytimes.com%2Fsearch%2Fsitesearch%2F%23%2Fobama%2Btests%2F>.

⁹⁷ V Putin, Op-ed: ‘A Plea for Caution from Russia’ (New York Times, 11 September 2013) <http://www.nytimes.com/2013/09/12/opinion/putin-plea-for-caution-from-russia-on-syria.html>.

⁹⁸ See S Lam, ‘China tells Washington to return to U.N. on Syria, urges caution’ (Reuters, 9 September 2013) <http://www.reuters.com/article/2013/09/09/us-syria-crisis-china-idUSBRE98804820130909>; ‘Brazil opposes military intervention in Syria without UN backing’ (China Daily, 28 August 2013) <http://www.chinadaily.com.cn/xinhua/2013-08-29/content_9986054.html>; CS Kasturi, ‘India opposes Syria action’ (The Telegraph (India), 31 August 2013) <http://www.telegraphindia.com/1130901/jsp/nation/story_17298146.jsp#.U2jxp1dRp8E>; Ministry of Foreign Affairs, Republic of Indonesia, ‘Indonesian President: Military Intervention in Syria Not the Right Solution’ (8 September 2013) <http://kemlu.go.id/Pages/News.aspx?IDP=6432&l=en>; ‘Factbox: Where G20 members stand on military action against Syria’ (Reuters, 6 September 2013) <http://www.reuters.com/article/2013/09/07/us-syria-crisis-g20-factbox-idUSBRE98602P20130907>.

⁹⁹ BBC News, ‘Syria crisis: Cameron loses Commons vote on Syria action’ (30 August 2013) <http://www.bbc.co.uk/news/uk-politics-23892783>.

¹⁰⁰ UNSC Resolution 2118 (2013) paras 4, 6 and 7.

¹⁰¹ Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226, para 47.

¹⁰² H Koh, ‘Syria and the Law of Humanitarian Intervention (Part II: International Law and the Way Forward)’ (EJIL Talk!, 4 October 2013) <http://www.ejiltalk.org/syria-and-the-law-of-humanitarian-intervention-part-ii-international-law-and-the-way-forward/>.