1 ILC Draft Articles on Responsibility of States for Internationally Wrongful Acts, 2001 YILC, Vol. 2 (Part Two), at 26–30.

2 1969 Vienna Convention on the Law of Treaties, 1155 UNTS 331.

3 R. Ago, Eighth Report, 1979 YILC, Vol. 2, 3 at 30.

4 Ibid., at 31, 37–8.

5 This statement is criticized in 3.2.2., infra.

6 See Ago's discussion of the cases of Savarkar (France v. Great Britain), Award of 24 February 1911, 11 RIAA 243; Russian Claim for Indemnities (Russia v. Turkey), Award of 11 November 1912, 11 RIAA 421; and Trial of the Major War Criminals before the International Military Tribunal (1947), Vol. 1, 171.

7 Important cases were the dispatching of troops by the United Kingdom to the Sultanate of Muscat and Oman in 1957 and to Jordan in 1958; by the United States to Lebanon in 1958; by Belgium to the Congo in 1964; and by the Soviet Union to Hungary in 1956, and to Czechoslovakia in 1968.

8 Ago referred to the discussions held before the Security Council concerning the presence of British armed forces in Greece during 1946, the presence of French and British troops in Syria and Lebanon despite the termination of hostilities in Europe and in the Far East, and the stationing of British forces in Egypt in accordance with the Anglo-Egyptian Treaty of 1936. See Ago, supra note 3, at 32–3.

9 For Ago, illustrative examples were the actions taken by West German counterterrorism forces at Mogadishu in 1977 and by Egyptian commandos at Larnaca in 1978.

10 For a detailed bibliography see Ago, supra note 3, at 34, note 151.

11 For a comprehensive bibliography see ibid.

12 See the comments made by Ushakov, Summary Records of the Thirty-First Session, 1542nd Meeting, 1979 YILC, Vol. 1, 44, at 46.

13 Summary Records of the Thirty-First Session, 1543rd Meeting, 1979 YILC, Vol. 1, 49 at 53.

14 Art. 2, subpara. 1(a) of the Vienna Convention on the Law of Treaties excludes unwritten agreements from the scope of the Convention. However, pursuant to Art. 3, paras. (a) and (b), this exclusion should neither prejudice the binding force of such agreements nor preclude the application thereupon of those rules whose validity is independent of the 1969 Convention.

15 Summary Records, 1543rd Meeting, supra note 13, at 50.

16 Ibid., at 51.

17 Ibid., at 50.

18 This definition of the notion of a rule is endorsed in Corbett, P., ‘The Consent of States and the Sources of the Law of Nations’, (1925) 6 BYIL 20Google Scholar, at 27–8; Fitzmaurice, G., ‘Some Problems Regarding the Formal Sources of International Law’, in van Asbeck, F.et al. (eds.), Symbolae Verzijl (1958), 153 at 158Google Scholar.

19 H. Kelsen, Principles of International Law (1952), 314, 417–18.

20 Kelsen, H., ‘Théorie générale du droit international public: Problèmes choisis’, (1932) 42 Recueil des cours 117, at 124–37Google Scholar.

21 ‘It is the essential function of any treaty to make law, that is to say, to create a legal norm, whether a general or an individual norm.’ Kelsen, supra note 19, at 319. However, Kelsen contradicts himself when he says,

Ibid., at 188.

22 This is Hart's criticism of Kelsen's vain attempts to fashion a basic norm for international law. See H. Hart, The Concept of Law (1994), 236.

23 Triepel, H., ‘Les rapports entre le droit interne et le droit international’, (1923) 1 Recueil des cours 73Google Scholar; Corbett, supra note 18, at 23; D. Anzilotti, Corso di Diritto Internazionale (1928), 73–6; K. Strupp, Eléments du droit international public universel, Européen et Américain (1930) and ‘Les règles générales du droit de la paix’, (1934) 47 Recueil des cours 259, at 263; Tunkin, G., ‘Remarks on the Judicial Nature of Customary Norms of International Law’, (1961) 49 California Law Review 419, at 422–3CrossRefGoogle Scholar; Cheng, B., ‘United Nations Resolutions on Outer Space: “Instant” Customary Law?’, (1965) 5 Indian Journal of International Law 23Google Scholar; Weil, P., ‘Towards Relative Normativity in International Law?’, (1983) 77 AJIL 413, at 420CrossRefGoogle Scholar. See also SS Lotus Case (France v. Turkey), 7 September 1927, PCIJ Rep Series A No. 10, at 18: ‘The rules of law binding upon States … emanate from their own free will’.

24 See H. Lauterpacht, The Function of Law in the International Community (2011), 426, 429–31.

25 H. Lauterpacht, International Law: Collected Papers, Vol. 2 (1970), at 92. Verdross too succumbs to transcendentalism when he holds that the basic norm of international law must be based on the universe of values and reason, on natural law. A. Verdross, Völkerrecht (1955), 23–5.

26 Lauterpacht, ibid., at 65–6.

27 Ross, A., A Textbook of International Law (1947), 95Google Scholar; Ago, R., ‘Positive Law and International Law’, (1957) 51 AJIL 691, at 716CrossRefGoogle Scholar.

28 Ago, ibid., at 720.

29 To the claim that international customary rules apply ipso facto to all states one may object by referring to the World Court's analysis of the existence of special custom in Case Concerning Right of Passage over Indian Territory (Portugal v. India), Judgment of 12 April 1960, [1960] ICJ Rep. 6; and in Asylum Case (Colombia v. Peru), Judgment of 20 November 1950, [1950] ICJ Rep. 266. True, in the mentioned cases, claims of a local or regional custom were considered and ultimately answered by the Court. But a closer look reveals that in those instances, the element of consent on the part of the state against which the existence of such a rule had been invoked played a vital role in the Court's reasoning. Thus, in those disputes, the Court erroneously applied the term local custom to situations which actually bore the hallmark of implicit agreement.

30 Fitzmaurice, supra note 18, at 157.

31 Corbett, supra note 18, at 28.

32 Akehurst, M., ‘Hierarchy of Norms in International Law’, (1974–75) 47 BYIL 273, at 275–6Google Scholar; R. Jennings and A. Watts (eds.), Oppenheim's International Law, Vol. 2 (1996), at 1275; J. Pauwelyn, Conflict of Norms in Public International Law: How WTO Law Relates to Other Rules of International Law (2003), 240–4; Tzanakopoulos, A., ‘Collective Security and Human Rights’, in de Wet, E. and Widmar, J. (eds.), Hierarchy in International Law (2012), 42 at 51Google Scholar.

33 This conclusion, which follows, in the first place, from considerations of principle, is confirmed by the fact that the precepts which are pertinent to determining the validity of treaties also apply to the question of validity of consent to conduct which, in the absence of such consent, would amount to an internationally wrongful act of the state. In both contexts, consent has to be valid, clearly established, really expressed, and attributable to the state.

34 Parties to a bilateral treaty may at any time agree to suspend or terminate the treaty. Likewise, a multilateral treaty can be suspended or terminated at any time by the consent of all the parties. Things are different when two contracting parties to a multilateral treaty seek the suspension of treaty relations as between themselves only. In such cases, for consent to operate as a circumstance precluding wrongfulness, it is required that certain procedures are followed. As to what these procedures are see 3.2.3., infra.

35 In the context of treaties, the rule which demands the adoption of certain conduct, in the last analysis, is always the pacta sunt servanda rule.

36 Introductory Commentary to Chapter III and Text of Draft Articles 16 and 19 with Commentaries thereto, adopted by the Commission at Its Twenty-Eighth Session, 1976 YILC, Vol. 2 (Part Two), 75 at 78.

37 Ibid.

38 J. Crawford, Second Report, 1999 YILC, Vol. 2, 3 at 12.

39 This line of reasoning is influenced by Fitzmaurice's circuitous comments on the distinction between suspension of treaty obligations and justified non-observance of treaty obligations. See G. Fitzmaurice, Fourth Report, 1959 YILC, Vol. 2, 37 at 46.

40 Crawford, Second Report, supra note 38, at 60 (references omitted). In agreement with Crawford, the following authors draw a line, as regards normative quality, between what they consider to be acts that are completely lawful and acts the wrongfulness of which is precluded pursuant to Chapter V in Part One of the Draft Articles: Alland, D., ‘Countermeasures of General Interest’, (2002) 13 EJIL 1221, at 1224CrossRefGoogle Scholar, notes 13 and 1233; Spiermann, O., ‘Humanitarian Intervention as a Necessity and the Threat or Use of Jus Cogens’, (2002) 71 Nordic Journal of International Law 523, at 526CrossRefGoogle Scholar and note 12 therein; Linderfalk, U., ‘State Responsibility and the Primary–Secondary Rules Terminology: The Role of Language for an Understanding of the International Legal System’, (2009) 78 Nordic Journal of International Law 53, at 66–8CrossRefGoogle Scholar. A similar trend can be observed in the works of George Fletcher, the man credited with rediscovering the importance of the distinction between justification and excuse in modern Anglo-American criminal law. According to Fletcher, ‘[j]ustified conduct in violation of the definition [of an offence] is not wrongful, but neither is it perfectly legal, as it is conduct that falls outside the scope of the definition’. Rethinking Criminal Law (2000), 576–7. In the following works, however, justified conduct is considered to be conduct which is perfectly lawful: Ross, A., On Guilt, Responsibility and Punishment (1975), 4, 107Google Scholar; Williams, G., ‘Offences and Defences’, (1982) 2 Legal Studies 233, at 239CrossRefGoogle Scholar; R. Bonnie et al., Criminal Law (1997), 324; Berman, M., ‘Justification and Excuse, Law and Morality’, (2003) 53 Duke Law Journal 1, at 29Google Scholar; H. Hart, Punishment and Responsibility (2008), 13–14. In the international context, the same conclusion is drawn in Pinto, M., ‘Reflections on International Liability for Injurious Consequences Arising out of Acts not Prohibited by International Law’, (1985) 16 NYIL 17, at 20CrossRefGoogle Scholar; Jagota, S., ‘State Responsibility: Circumstances Precluding Wrongfulness’, (1985) 16 NYIL 249, at 254CrossRefGoogle Scholar; Kohen, M., ‘The Notion of “State Survival” in International Law’, in de Chazournes, L. Boisson and Sands, P. (eds.), International Law, the International Court of Justice and Nuclear Weapons (1999), 293 at 308–10Google Scholar; Lowe, V., ‘Precluding Wrongfulness or Responsibility: A Plea for Excuses’, (1999) 10 EJIL 405, at 406CrossRefGoogle Scholar (while recognizing that the circumstances in Chapter V are situations of negation of obligation, Lowe goes on to argue that it is preferable to maintain the binding pull of obligation and instead excuse its breach).

41 Summary Records of the 2567th Meeting, 1999 YILC, Vol. 1, 4 at 6–7. Case Concerning the Difference between New Zealand and France Concerning the Interpretation or Application of Two Agreements, Concluded on 9 July 1986 between the two States and Which Related to the Problems Arising from the Rainbow Warrior Affair, Award of 30 April 1990, 20 RIAA 215, at 251 (emphasis added).

42 Gabčíkovo-Nagymaros Project (Hungary v. Slovakia), Judgment of 25 September 1997, [1997] ICJ Rep. 7, at 39, para. 48 (emphasis added).

43 Crawford, Second Report, supra note 38, at 61–2. The same position is endorsed in Abass, A., ‘Consent Precluding State Responsibility: A Critical Analysis’, (2004) 53 ICLQ 211, at 224CrossRefGoogle Scholar; Christakis, T. and Bannelier, K., ‘Volenti Non Fit Injuria? Les effets du consentement à l’intervention militaire’, (2005) 50 Annuaire Français de droit international 102, at 107CrossRefGoogle Scholar et seq.; T. Christakis, ‘Les “circonstances excluant l’illicéité”: Une illusion optique?’, in Droit du pouvoir, pouvoir du droit: Mélanges offerts à Jean Salmon (2007), 223 at 244–51; O. Corten, The Law against War: The Prohibition on the Use of Force in Contemporary International Law (2010), 250–1; Ben Mansour, A., ‘Circumstances Precluding Wrongfulness in the ILC Articles on State Responsibility: Consent’, in Crawford, J., Pellet, A., and Olleson, S. (eds.), The Law of International Responsibility (2010), 439 at 440Google Scholar; S. Szurek, ‘The Notion of Circumstances Precluding Wrongfulness’, in ibid. 427 at 430.

44 Crawford, Second Report, supra note 38, at 63.

45 Draft Articles on Responsibility of States for Internationally Wrongful Acts with Commentaries, adopted by the Commission at Its Fifty-Third Session, 2001 YILC, Vol. 2 (Part Two), 31 at 72–3 (references omitted and emphasis added).

46 Ibid., at 85 (references omitted and emphasis added).

47 For some time now, it has been fashionable to ascribe the primary-rule–secondary-rule terminology in the Commission's study of the law of state responsibility to Herbert Hart's The Concept of Law. See, e.g., Scobbie, I., ‘Assumptions and Presumptions: State Responsibility for System Crimes’, in Nollkaemper, A. and van der Wilt, H. (eds.), System Criminality in International Law (2009), 270 at 272CrossRefGoogle Scholar; David, E., ‘Primary and Secondary Rules’, in Crawford, J., Pellet, A., and Olleson, S. (eds.), The Law of International Responsibility (2010), 27 at 28Google Scholar; T. Ruys, Armed Attack and Article 51 of the UN Charter: Evolutions in Customary Law and Practice (2010), 489; J. d’Aspremont, Formalism and the Sources of International Law (2011), 51. The Hartian principle of rule classification, however, is not analogous with the scheme by means of which Ago defined the orbit of the study of the law of state responsibility. The inspiration for the latter is the writings of Alf Ross. See Ross, supra note 27, at 77, 241–2, 271–3. See also A. Ross, On Law and Justice (1958), 207–11 and Directives and Norms (1968), 113–15. This has been acknowledged in Goldie, L., ‘State Responsibility and the Expropriation of Property’, (1978) 12 International Lawyer 63, at 65–6Google Scholar; Dugard, J., Second Report, 2001 YILC, Vol. 2, 97 at 101Google Scholar; Spiermann, O., ‘A National Lawyer Takes Stock: Professor Ross’ Textbook and Other Forays into International Law’, (2003) 14 EJIL 675, at 697CrossRefGoogle Scholar.

48 There are international obligations, particularly in the field of humanitarian law, whose complete definition excludes the possibility of invoking any of the circumstances precluding wrongfulness. The prohibitions on genocide, torture, and apartheid can be given as prime examples of such obligations.

49 Draft Articles with Commentaries, supra note 45, at 72. The centrality of this rule in international judicial proceedings is confirmed in M. Kazazi, Burden of Proof and Related Issues: A Study on Evidence before International Tribunals (1996), 221–3; Wolfrum, R., ‘Taking and Assessing Evidence in International Adjudication’, in Ndiaye, T. and Wolfrum, R. (eds.), Law of the Sea, Environmental Law and Settlement of Disputes: Liber Amicorum Judge Thomas A. Mensah (2007), 341 at 344–5CrossRefGoogle Scholar.

50 Art. 53, Vienna Convention on the Law of Treaties.

51 It is recalled from 3.2., supra, that Crawford tried but ultimately failed to bring about the deletion of the provision dealing with consent as a circumstance precluding wrongfulness.