¹ UN Charter, art 51, does not mention ‘proportionality’/‘proportionate’ at all, and ‘necessity’/‘necessary’ only in relation to the Security Council: cf art 51(1): ‘… until the Security Council has taken measures necessary to maintain international peace and security’.

² Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, 8 July 1996 [1996] ICJ Rep 226 (‘Nuclear Weapons’), [41] (citing Military and Paramilitary Activities in and Against Nicaragua, Merits, Judgment, 27 June 1986 [1986] ICJ Rep 14 (‘Nicaragua’), [176]). The fullest account of the ICJ's jurisprudence on self-defence can be found in Green, James A, The International Court of Justice and Self-Defence (Hart 2009)Google Scholar.

³ Oil Platforms (Islamic Republic of Iran v US), Judgment, 6 November [2003] ICJ Rep 161 (‘Oil Platforms’), [76]. In its work on state responsibility, the International Law Commission (ILC) even suggested that ‘the requirements of proportionality and of necessity [were] inherent in the notion of self-defence’: Responsibility of States for Internationally Wrongful Acts (2001), annexed to UNGA Res 56/83, 12 December 2001, and reproduced in Crawford, James (ed), The ILC's Articles on State Responsibility (CUP 2002)Google Scholar], commentary to art 21, para 6. See further Gray, Christine D, International Law and the Use of Force (3^rd edn, OUP 2008) 147Google Scholar; Gardam, Judith Gail, Proportionality, Necessity and the Use of Force in International Law (CUP 2004) 138ffCrossRefGoogle Scholar; Roucounas, ‘Emmanuel, ‘Preliminary Report on Self-Defence’ (2007) Annuaire de l'Institut de droit international 72, 99Google Scholar.

⁴ Both necessity and proportionality come ‘in a number of different guises and forms’: Lubell, Noam, Extraterritorial Use of Force against Non-State Actors (OUP 2010) 64CrossRefGoogle Scholar. In addition to the jus ad bellum, they operate as restraints under rules governing the conduct of hostilities, or jus in bello. Proceedings such as Nuclear Weapons (n 2) suggest that the two different sets of limitations are not always clearly separated, and frequently an unnecessary use of force may equally violate the jus in bello. That, however, is not necessarily the case, and the two tests follow a different rationale – the jus ad bellum regulates the entitlement and scope to use force, whereas necessity and proportionality under the jus in bello govern the employment of force in concrete military encounters, such as issues of targeting. These latter considerations will largely be left to a side in the following, and taken up only to the extent that they influence the necessity and proportionality tests under the jus ad bellum. For a useful discussion see Cannizaro, Enzo, ‘Contextualizing Proportionality: Jus ad Bellum and Jus in Bello in the Lebanese War’ (2006) 88 International Review of the Red Cross 779CrossRefGoogle Scholar.

⁵ Nuclear Weapons (n 2) [41].

⁶ Especially given the position taken by the ICJ in Legal Consequences of the Construction of a Wall in Occupied Palestinian Territory, Advisory Opinion, 9 July 2004, [2004] ICJ Rep 136 (‘Wall’), [139]; cf the Separate Opinion of Judge Higgins, [33]–[35] and the Declaration of Judge Buergenthal, [6], as well as the following voices in the literature: Cassese, Antonio, ‘Terrorism is also Disrupting Some Crucial Legal Categories of International Law’ (2001) 12 European Journal of International Law 993CrossRefGoogle Scholar; Stahn, Carsten, ‘Nicaragua is Dead, Long Live Nicaragua!’ in Walter, Christian and others (eds), Terrorism as a Challenge for National and International Law: Security versus Freedom? (Springer 2004) 827Google Scholar; Kammerhofer, Jörg, ‘The Armed Activities Case and Non-State Actors in Self-Defence Law’ (2007) 20 Leiden Journal of International Law 89CrossRefGoogle Scholar; Tomuschat, Christian, ‘Der 11 September und seine rechtlichen Konsequenzen’ (2001) 28 Europäische Grundrechte-Zeitschrift 535Google Scholar; Murphy, Sean D, ‘Self-Defense and the Israeli Wall Opinion – An Ipse Dixit from the Court?’ (2005) 99 American Journal of International Law 62CrossRefGoogle Scholar and ‘Terrorism and the Concept of “Armed Attack” in Article 51 of the UN Charter’ (2002) 43 Harvard International Law Journal 41Google Scholar; Krajewski, Markus, ‘Selbstverteidigung gegen bewaffnete Angriffe nicht-staatlicher Organisationen’ (2002) 40 Archiv des Völkerrechts 183Google Scholar; Ruys, Tom and Verhoeven, Sten, ‘Attacks by Private Actors and the Right of Self-Defence’ (2005) 10 Journal of Conflict and Security Law 289CrossRefGoogle Scholar; Antonopoulos, Constantine, ‘Force by Armed Groups as Armed Attack and the Broadening of Self-Defence’ (2008) 55 Netherlands International Law Review 159CrossRefGoogle Scholar; Klein, Pierre, ‘Le droit international à l'épreuve du terrorisme’, 321 Recueil des Cours (2006) 396ffGoogle Scholar; Gray (n 3) 193ff); van Steenberghe, Raphaël, ‘Self-Defence in Response to Attacks by Non-State Actors in the Light of Recent State Practice: A Step Forward?’ (2010) 23 Leiden Journal of International Law 183CrossRefGoogle Scholar; Moir, Lindsay, Reappraising the Resort to Force (Hart 2010), especially 22–31Google Scholar; Tsagourias, Nicholas, ‘Non-State Actors in International Peace and Security: Non-State Actors and the Use of Force’ in d'Aspremont, Jean (ed), Participants in the International Legal System: Multiple Perspectives on Non-State Actors in International Law (Routledge 2011) 326Google Scholar.

⁷ See references in n 6. For Tams' view on the matter see Tams, Christian J, ‘The Use of Force against Terrorists’ (2009) 20 European Journal of International Law 359Google Scholar; Tams, Christian J, ‘Light Treatment of a Complex Problem’ (2005) 16 European Journal of International Law 963CrossRefGoogle Scholar; Tams, Christian J, ‘Swimming with the Tide, or Seeking to Stem It? Recent ICJ Rulings on the Law of Self-Defence’ (2005) 18 Revue Québécoise de Droit International 275Google Scholar; and Bruha, Thomas and Tams, Christian J, ‘Self-Defence against Terrorist Attacks. Considerations in the Light of the ICJ's Israeli Wall Opinion’ in Dicke, K and others (eds), Weltinnenrecht. Liber Amicorum Jost Delbrück (Duncker and Humblot 2005) 85Google Scholar.

⁸ According to Judge Kooijmans, ‘this has been the generally accepted interpretation for more than 50 years’, which anti-terrorist practice had called into question: see Wall (n 6), Separate Opinion of Judge Kooijmans, [35].

⁹ Nicaragua (n 2) [109] and [115].

¹⁰ See Responsibility of States for Internationally Wrongful Acts (n 3), commentary to art 8(3)–(5).

¹¹ For references cf Gray (n 3) 99–103.

¹² In addition to the states involved in the instances mentioned in the text (Israel, US, Turkey), these include, for example, the following: Australia, Russia, Iran, Colombia, and states participating in Operation Enduring Freedom. For references see Tams, ‘The Use of Force against Terrorists’ (n 7) 378–81.

¹³ See references ibid.

¹⁴ See the detailed account by Ruys, Tom, ‘Quo Vadit Jus ad Bellum? A Legal Analysis of Turkey's Military Operations against the PKK in Northern Iraq’, (2008) 12 Melbourne Journal of International Law 334Google Scholar; and further Wettberg, Gregor, The International Legality of Self-Defence Against Non-State Actors (European University Studies 2007) 144–51Google Scholar for details.

¹⁵ Ruys (n 14) 344.

¹⁶ For example, the Belgian Foreign Minister noted that the Turkish action ‘was precisely targeted and aimed only at PKK targets, without harming the population of northern Iraq or local factions’: Questions et réponses écrites, Chambre des représentants de Belgique, 25 February 2008, QRVA 52 010, 1357; available at http://www.dekamer.be/QRVA/pdf/52/52K0010.pdf. His Dutch colleague observed that ‘the Turkish actions appear to be restricted to specific actions against PKK targets in the border area of northern Iraq’: Maxime Verhagen, ‘Beantwoording vragen van het lid Van Bommel over een Turkse invasie in Noord-Irak’, Ministerial statement, 3 March 2008, as cited in Ruys (n 14) 363.

¹⁷ See UN Doc A/60/937-S/2006/515, Letter sent to the Security Council dated 12 July 2006. For a comprehensive account see Ronen, Yaël, ‘The 2006 Conflict in Lebanon’ (2008) 9 Yearbook of International Humanitarian Law 362–93CrossRefGoogle Scholar; see also Secretary-General's Report on UNIFIL, UN Doc S/2006/560, 22 July 2006; and Gray (n 3) 237–44. For a detailed legal analysis cf Zimmermann, Andreas, ‘The Second Lebanon War: Jus ad Bellum, Jus in Bello and the Issue of Proportionality’ (2007) 11 Max Planck Yearbook of United Nations Law 99Google Scholar; and Cannizaro (n 4) 779.

¹⁸ States including Russia, Argentina, Japan and France: see UN Doc S/PV.5488, 13 July 2006; UN Doc S/PV.5489, 14 July 2006; UN Doc S/PV.5493, 21 July 2006; UN Doc S/PV.5493 (Resumption 1), 21 July 2006.

¹⁹ Van Steenberghe (n 6) 193. During the Security Council meeting of 14 July 2006, only China and Qatar expressly rejected Israel's reliance on self-defence: see UN Doc S/PV 5489. In contrast, Israel's right was recognised by Argentina (ibid 9), Japan (12), the UK (12), Peru (14), Denmark (15), Slovakia (16), Greece (17), France (17) and the USA (17). The UN Secretary General also acknowledged Israel's right to defend itself against Hezbollah attacks under UN Charter, art 51: see UN Doc S/PV.5492, 20 July 2006, 3; UN Doc S/PV.5498, 30 July 2006, 3.

²⁰ For a clear account see Lobel, Jules, ‘The Use of Force to Respond to Terrorist Attacks: The Bombing of Sudan and Afghanistan’ (1999) 24 Yale Journal of International Law 537Google Scholar.

²¹ UN Doc S/1998/780, 20 August 1998.

²² China, Russia, a number of Arab states and the Non-Aligned Movement condemned it, as did (at least implicitly) UN Secretary General Kofi Annan: cf Schneider, Howard and Boustany, Nora, ‘A Barrage of Criticism in Mideast; US Accused of “State Terrorism”’, Washington Post (21 August 1998) A20Google Scholar.

²³ See Lobel (n 20) 556–57, for much more on this point; and Wettberg (n 14) 157–59, for a summary of responses.

²⁴ See the references in Drozdiak, William, ‘European Allies Back US Strikes; Japan Says It “Understands”’, Washington Post (21 August 1998)Google Scholar A20.

²⁵ For references to, and controversial assessments of, many other instances, see the works cited in nn 6 and 7.

²⁶ These are very clearly set out in the works by Gray (n 3) and Klein (n 6) as well as Corten, Olivier, ‘Self-Defence Against Terrorists: What can be Learned from Recent Practice (2005–2010)?’ (2010) 109 Kokusaiho Gaiko Zassi (Journal of International Law and Diplomacy) 129Google Scholar.

²⁷ See the position taken by the ICJ in Wall (n 6) [139].

²⁸ On this compare, for example, Trapp, Kimberley N, ‘The Use of Force against Terrorists: A Reply to Christian J. Tams’ (2009) 20 European Journal of International Law 1049CrossRefGoogle Scholar and Tams, Christian J, ‘The Use of Force against Terrorists: A Rejoinder to Federico Sperotto and Kimberley N. Trapp’, (2009) 20 European Journal of International Law 1057Google Scholar.

²⁹ Nuclear Weapons (n 2) [41] (emphasis added).

³⁰ Gardam (n 3) 148–50; Gray (n 3) 150; Gazzini, Tarcisio, The Changing Rules on the Use of Force in International Law (Manchester University Press 2006)Google Scholar 146.

³¹ cf the British–American correspondence relating to the Caroline incident (Note from Mr Webster to Mr Fox, 24 April 1841) in 29 BFSP 1129, 1138 (1840–41) (‘the Caroline correspondence’).

³² See Ago, Roberto, Eighth Report on State Responsibility (Addendum), Yearbook of the International Law Commission 1980, vol II/1, 60Google Scholar, para 120: ‘The reason for stressing that action taken in self-defence must be necessary is that the state attacked (or threatened with imminent attack, if one admits preventive self-defence) must not, in the particular circumstances, have had any means of halting the attack other than recourse to armed force. In other words, had it been able to achieve the same result by measures not involving the use of armed force, it would have no justification for adopting conduct which contravened the general prohibition against the use of armed force. The point is self-evident and is generally recognized; hence it requires no further discussion’ (emphasis added).

³³ This latter qualification is frequently overlooked. See, however, the very clear formulation in Principle 3 of the Chatham House Principles: Wilmshurst, Elizabeth, ‘Principles of International Law on the Use of Force by States in Self-Defence’, Chatham House, ILP WP 05/01, October 2005; reproduced in (2006) 55 International and Comparative Law Quarterly 963 (‘Chatham House Principles’)CrossRefGoogle Scholar.

³⁴ See commentary to Principle 3 of the Chatham House Principles, ibid.

³⁵ Dinstein, Yoram, War, Aggression, Self-Defence (4^th edn, CUP 2005) 237CrossRefGoogle Scholar; Schachter, Oscar, International Law in Theory and Practice (Martinus Nijhoff 1991) 152Google Scholar.

³⁶ This approach has remained controversial, but would seem to follow from the ICJ's jurisprudence in Nicaragua (n 2) [191], Oil Platforms (n 3) [51] and [62], and Armed Activities on the Territory of the Congo (Democratic Republic of Congo (DRC) v Uganda) Judgment, 19 December 2005 [2005] ICJ Rep 201 (‘DRC v Uganda’) [147]). See also the Eritrea/Ethiopia Boundary Commission's Award on Ethiopia's Jus ad Bellum Claims 1–8, 19 December 2005 (2006) 45 ILM 430. For details see Green (n 2) 31–41; and for a useful summary van Steenberghe (n 6) 202–04.

³⁷ This implies a general statement on the relationship between self-defence and collective security measures, expressing the Charter's preference for ‘institutional’ action over ‘private’ reactions: cf Stanimir Alexandrov, A, Self-Defense against the Use of Force in International Law (Kluwer 1996) 104–05Google Scholar and 130ff for details and references.

³⁸ The point is much neglected. For comment see Dinstein (n 35) 215–16; Gray (n 3) 126–28.

³⁹ Dinstein (n 35) 216.

⁴⁰ Hence the Security Council's determination, in SC Res 502 (1982), that Argentina's invasion of the Falklands/Malvinas amounted to a breach of the peace was as such not sufficient to disapply the UK's right of self-defence. See further Gray (n 3) 125.

⁴¹ UNSC Res 661(1990), UN Doc S/RES/661, 6 August 1990.

⁴² This in fact was already envisaged by Kelsen, Hans, The Law of the United Nations (2nd edn, Stevens & Sons 1951) 800–02Google Scholar.

⁴³ See SC Res 1701(2006), 11 August 2006, which required Hezbollah to cease all attacks and Israel to refrain from ‘all offensive military operations’ (emphasis added). For debates about the scope of this disapplication of self-defence see UN Doc S/2007/147, 14 March 2007, at 3–8; for a discussion of the status of the resolution (which did not mention ‘Chapter VII’ directly but used the language of art 39) see Lapidoth, Ruth, ‘The Legal Effect of Security Council Resolution 1701 (2006) on Cessation of Hostilities in Lebanon’ in Fischer-Lescano, Andreas and others (eds), Frieden in Freiheit = Peace in liberty = Paix en liberté: Festschrift für Michael Bothe zum 70. Geburtstag (Nomos/Dike 2008)Google Scholar 187).

⁴⁴ Noam Lubell, ‘Use of Force against Individuals and Groups Abroad’, PhD thesis, University of Essex (2008) at 47. The formulation does not seem to be used in Lubell (n 4).

⁴⁵ cf Caroline correspondence (n 31).

⁴⁶ See Principle 6 of the Chatham House Principles (n 33): ‘If the right of self-defence … is to be exercised in the territory of another state, it must be evident that that state is unable or unwilling to deal with the non-state actors itself, and that it is necessary to use force from outside to deal with the threat in circumstances where the consent of the territorial state cannot be obtained’.

⁴⁷ This is brought out implicitly through the fact that in order to justify their conduct, states asserting a right to use self-defence against terrorist attacks stressed that host states had taken no action. Hence in order to justify their conduct in the instances mentioned above in Section 2 ‘Background’, Turkey and the US asserted that the respective host states affected by their operations had been unwilling or unable to prevent the terrorist threat or attack. Israel went further in that it alleged (controversially) that Lebanon had supported Hezbollah's activities and therefore bore responsibility.

⁴⁸ Principle 6 of the Chatham House Principles (n 33); and further Ruys and Verhoeven (n 6) 316.

⁴⁹ Paust, Jordan J, ‘Use of Force against Terrorists in Afghanistan, Iraq and Beyond’ (2002) 35 Cornell International Law Journal 533, 540–43Google Scholar.

⁵⁰ Ruys and Verhoeven (n 6) 317.

⁵¹ cf Sarah Rainsford, ‘Iraq Troop Withdrawal Baffles Turks’, BBC News (UK) 29 February 2008, available at http://news.bbc.co.uk/2/hi/europe/7272108.stm.

⁵² See, for example, Letter from the Permanent Representative of the Russian Federation to the United Nations addressed to the Secretary-General, UN Doc S/2002/1012, 11 September 2002 (seeking to justify Russia's use of force on Georgian territory and claiming that ‘[t]he continued existence in separate parts of the world of territorial enclaves outside the control of national governments, which, owing to the most diverse circumstances, are unable or unwilling to counteract the terrorist threat is one of the reasons that complicate efforts to combat terrorism effectively’). Iran has on several occasions invoked UN Charter art 51 to justify the use of force against bases of the Mujahedin-e Khalq Organization (MKO) on Iraqi territory – see Wandscher, Christiane, Internationaler Terrorismus und Selbstverteidigungsrecht (Duncker & Humblot 2006) 148–49Google Scholar; Wettberg (n 14) 151–52. While Iraq denounced the use of force as an act of aggression, the international community did not condemn it. Similarly, Iran's incursions into Iraqi territory in pursuit of Kurdish armed bands (labelled ‘organized terrorist mercenaries’) avoided international criticism: see Franck, Thomas, Recourse to Force (CUP 2002)CrossRefGoogle Scholar 64. There was little evidence to suggest that the conduct of the MKO (let alone that of Kurdish insurgents) could have been attributed to Iraq.

⁵³ See explanation to Principle 6 of the Chatham House Principles (n 33).

⁵⁴ See UNGA Res 2625(XXV), 24 October 1970, Principle I (10); ICJ, Corfu Channel Case, Judgment, 9 April 1949, [1949] ICJ Rep 4.

⁵⁵ cf art 1(c)(xi): ‘The following shall constitute acts of aggression: (…) the encouragement, support, harbouring or provision of any assistance for the commission of terrorist acts and other violent transnational organized crimes against a Member state’; available at http://www.africa-union.org/root/au/documents/treaties/text/Non%20Aggression%20Common%20Defence%20Pact.pdf.

⁵⁶ Notably in the case of the Taliban and Al Qaeda: see, for example, UNSC Res 1214(1998), UN Doc S/RES/1214, 8 December 1998; and UNSC Res 1267(1999), UN Doc S/RES/1267, 15 October 1999.

⁵⁷ For example, the specific obligations relating to the suppression of PKK activities under the 1999 Washington Accord. For details see Ruys (n 14).

⁵⁸ nn 17–19.

⁵⁹ See, for example UN Doc S/2002/1012 (n 52) in respect of Russia's claim referred to above; and cf Tams, ‘The Use of Force against Terrorists’ (n 7) 379–81 for a summary of similar claims.

⁶⁰ A point rightly stressed in the comment to Principle 6 of the Chatham House Principles (nn 33 and 46).

⁶¹ See below, Section 6 ‘Anti-Terrorist Proportionality’.

⁶² A point rightly stressed by Lobel (n 20) 552–53.

⁶³ Roucounas (n 3) 99.

⁶⁴ Trapp, Kimberley N, ‘Back to Basics: Necessity, Proportionality, and the Right of Self-Defence against Non-State Terrorist Actors’ (2007) 56 International and Comparative Law Quarterly 141, 146CrossRefGoogle Scholar; Green (n 2) 86; Lubell (n 4) 63–64.

⁶⁵ See Delbrück, Jost, ‘Proportionality’ in Bernhardt, R (ed), Encyclopedia of Public International Law, vol III (1997), 1140Google Scholar; and the detailed treatment by Franck, Thomas, ‘On Proportionality of Countermeasures in International Law’ (2008) 102 American Journal of International Law 715CrossRefGoogle Scholar.

⁶⁶ A point rightly stressed by Lubell (n 4) 63–64.

⁶⁷ See Nuclear Weapons (n 2) [42]; Lubell (n 4), 63–64; and cf above n 4.

⁶⁸ For the ICJ's approach see the following two statements made in the Nicaragua and DRC v Uganda cases: (i) ‘Whatever uncertainty may exist as to the exact scale of the aid received by the Salvadorian opposition from Nicaragua, it is clear that these … United States activities … could not have been proportionate to that aid.’ (Nicaragua (n 2) [237]); (ii) ‘[T]he taking of airports and towns many hundreds of kilometres from Uganda's border would not seem proportionate to the series of transborder attacks it claimed had given rise to the right of self-defence’ (DRC v Uganda (n 36) [147]). For comment, see notably Christodoulidou, Theodora and Chainoglou, Kalliopi, ‘The Principle of Proportionality in Self-Defence and Humanitarian Intervention’ (2007) 20 Humanitäres Völkerrecht 79, 83Google Scholar: ‘The above analysis of [ICJ jurisprudence] seems to argue that the ICJ's approach to proportionality, albeit epigrammatically at times, is to strike a balance between the attack and the wrong provoking it.’ See also Frederic L Kirgis, ‘Some Proportionality Issues Raised by Israel's Use of Armed Force in Lebanon’, ASIL Insight No 10/2006: ‘These ICJ pronouncements focus primarily on weighing the intensity of the defensive force against the intensity of the force defended against.’ Available at http://www.asil.org/insights060817.cfm#_ednref3.

⁶⁹ Cannizaro (n 4) 785.

⁷⁰ The point may be illustrated by reference to the Falklands/Malvinas conflict of 1982, during which the British self-defence operation led to the loss of 907 lives, compared to 0 lives lost during Argentina's invasion; and still it was not seriously considered to be disproportionate.

⁷¹ Principle 5 of the Chatham House Principles (n 33).

⁷² For details and useful comment see notably Gardam (n 3) 159–79.

⁷³ cf O'Connell, Daniel Patrick, The Influence of Law on Sea Power (Manchester University Press 1975)Google Scholar 64.

⁷⁴ cf Wettberg (n 14) 144–51, for details. cf Rainsford (n 51).

⁷⁵ cf Cabinet Communiqué of 16 July 2006: ‘Prime Minister Olmert said that we would continue in this campaign as necessary and added that it is clear to all that we will not stop until we can tell the Israeli people that the threat hanging over it has been removed.’ Available at http://www.mfa.gov.il/MFA/Government/Communiques/2006/Cabinet+Communique+16-Jul-2006.htm.

⁷⁶ Gray (n 3) 197. See Lobel (n 20) 537, for details.

⁷⁷ See Gill, TD, ‘The Temporal Dimension of Self-Defence: Anticipation, Pre-Emption, Prevention and Immediacy’ (2006) 11 Journal of Conflict and Security Law 361CrossRefGoogle Scholar; Hamid, Abdul Ghafur, ‘The Legality of Anticipatory Self-Defence in the 21^st Century World Order’ (2007) 54 Netherlands International Law Review 441CrossRefGoogle Scholar; and Gray (n 3) 160ff.

⁷⁸ Whether such an ‘accumulation of events’ triggers a right of self-defence is much discussed: for a clear summary of debates see, for example, Gray (n 3) 155; and cf the ICJ's statement, in Oil Platforms (n 3) [64] that ‘even taken cumulatively’ a series of incidents did not qualify as an armed attack on the United States. Since the question primarily concerns the interpretation of the ‘armed attack’ requirement, it is left to a side here. It should, however, be noted that recognition of the doctrine would help to avoid the sometimes artificial separation of multiple attacks into separate incidents; on the other hand, it would risk turning self-defence into an open-ended licence to use counterforce.

⁷⁹ Daniel Bethlehem, ‘International Law and the Use of Force: The Law As It Is and As It Should Be’, written evidence to the Select Committee on Foreign Affairs, Minutes of Evidence, 8 June 2004, para 21; available at http://www.publications.parliament.uk/pa/cm200304/cmselect/cmfaff/441/4060808.htm.

⁸⁰ cf Gardam (n 3) 187.

⁸¹ See Section 4, ‘Anti-terrorist necessity’.

⁸² For much more on this process see Franck (n 65).

⁸³ cf Gray (n 3) 154, who notes that proportionality has come to be seen as a convenient yardstick against which states' responses can be assessed – precisely so as to avoid complex debates about the availability of self-defence: ‘In Security Council debates states have thus been able to avoid going into doctrinal disputes as to whether self-defence is wide or narrow; they can simply say that the use of force was not necessary or proportionate and therefore illegal.’

⁸⁴ The Turkish military claimed that approximately 540 PKK members were killed during the bombardments and the ground offensive, which also led to the destruction of 800 shelters, weapon stores and other PKK positions.

⁸⁵ See n 16.

⁸⁶ In fact, it is telling that after a detailed study, one commentator observed that ‘the Turkish intervention poses few problems in terms of proportionality’: Ruys (n 14) 344.

⁸⁷ Trapp (n 64) 155.

⁸⁸ For statements to this effect see, for example, UN Doc S/PV.5492, 20 July 2006, 3 (Secretary-General) or UN Doc S/PV.5489, 30 July 2006, 9 (Argentina).

⁸⁹ Franck (n 65) 764: ‘Dispute by dispute and adjudication by adjudication … international law is developing rather like the common law, broadening precedent by precedent.’