1 Gabcikovo-Nagymaros Project (Hungary/Slovakia), Judgment of 25 September 1997, [1997] ICJ Rep. 7, at 124, para. 16 (Judge Bedjaoui, Separate Opinion).

2 See M. Koskenniemi, Fragmentation of International Law: Difficulties Arising from the Diversification and Expansion of International Law, Report of the Study Group of the International Law Commission, UN Doc. A/CN.4/L.682 (2006), at 241.

3 South West Africa (Ethiopia v. South Africa; Liberia v. South Africa), Second Phase, Judgment of 18 July 1966, [1966] ICJ Rep. 6, at 439 (Judge Jessup, Dissenting Opinion).

4 See Report of the International Law Commission, UN Doc. A/63/10 (2008), at 355. For the establishment and orientation of the ILC Study Group on Treaties over Time, see Report of the International Law Commission, UN Doc. A/64/10 (2009), at 353–5.

5 Case Concerning the Dispute Regarding Navigational and Related Rights (Costa Rica v. Nicaragua), Judgment of 13 July 2009 (hereinafter Judgment), available at www.icj-cij.org.

6 Costa Rica–Nicaragua Treaty of Limits (Cañas-Juárez), signed at Managua, 6 July 1857, available at http://manfut.org/cronologia/t-canasjuarez.html.

7 Costa Rica–Nicaragua, Convention of Peace (Cañas-Martínez), 49 BFSP 1222 (1857) (Arts. 8 and 9 subject to ratification; remainder in force on signature).

8 For a brief history of the dispute, see Judgment, supra note 5, paras. 15–29.

9 Judgment, supra note 5, para. 44 (ICJ translation).

10 For a brief discussion, see Judgment, supra note 5, paras. 20, 22, and 49. In the Cleveland Award, having determined that the Treaty of Limits was valid, President Cleveland found that its Art. VI did not allow Costa Rica to navigate the San Juan River with vessels of war; by contrast, Costa Rica was allowed to navigate the river with vessels of the Revenue Service in so far as they were connected with navigation ‘for purposes of commerce’. But nothing was said about the putative navigation rights of other Costa Rican public vessels. On the application of Costa Rica, the Central American Court of Justice found that Nicaragua had violated Art. VIII of the Treaty of Limits and the Cleveland Award by entering into the 1914 Chamorro-Bryan Treaty with the United States (relating to an inter-oceanic canalization project through the San Juan River) without consulting Costa Rica prior to the conclusion of that agreement (see ibid.).

11 Judgment, supra note 5, para. 41.

12 Costa Rica Memorial (hereinafter CRM), para. 3.01; Verbatim Record, 2 March 2009, CR 2009/2 (uncorrected), 23, para. 2 (Mr Ugalde on behalf of Costa Rica), available at www.icj-cij.org.

13 CRM, ibid., para. 4.64; Verbatim Record, 34, para. 53 (Mr Kohen on behalf of Costa Rica).

14 Judgment, supra note 5, para. 24.

15 For Costa Rica's submissions, see Judgment, supra note 5, paras. 12–14.

16 Judgment, supra note 5, paras. 12(b) and 13 (emphasis added).

17 Judgment, supra note 5, para. 45.

18 Judgment, supra note 5, para. 58. The element of the intention of the parties is not explicitly stated in Arts. 31–2 VCLT but the ILC commentary is full of references thereto; see, e.g., para. 11 of the commentary to what became Arts. 31–2 VCLT, 1966 YILC, Vol. II, at 220. For affirmation of this basic principle, see further, e.g., Award in the Arbitration Regarding the Iron Rhine Railway between the Kingdom of Belgium and the Kingdom of the Netherlands, Award of 24 May 2005, RIAA, Vol. XXVII, 35, at 65, para. 53; Interpretation of the Convention of 1919 Concerning Employment of Women during the Night, Advisory Opinion of 15 November 1932, PCIJ Rep., Series A/B, No. 50, 365, at 383 (Judge Anzilotti, Dissenting Opinion); R. Jennings and A. Watts (eds.), Oppenheim's International Law (1992), 1267; I. Brownlie, Principles of Public International Law (2008), 631; A. D. McNair, The Law of Treaties (1961), 365; I. Sinclair, The Vienna Convention on the Law of Treaties (1984), 134–5; P. Reuter, Introduction au droit des traités (1995), 88, para. 141.

19 For a recent affirmation of the textual approach, see Legality of Use of Force (Serbia and Montenegro v. Belgium), Preliminary Objections, Judgment of 15 December 2004, [2004] ICJ Rep. 279, at 318, para. 100 (‘Interpretation must be based above all upon the text of the treaty’).

20 Judgment, supra note 5, para. 47 (since Nicaragua is not a party to the VCLT, it was necessary for the Court to make this point). For the most recent reaffirmation by the Court, see Pulp Mills on the River Uruguay (Argentina v. Uruguay), Judgment of 20 April 2010, para. 64.

21 Nicaragua Countermemorial (hereinafter NCM), para. 4.3.11 (emphasis in original).

22 G. Fitzmaurice, ‘The Law and Procedure of the International Court of Justice 1951–4: Treaty Interpretation and Other Treaty Points’, (1957) 33 BYIL 203, at 212 and 225–7.

23 For references to the ‘principle of contemporaneity’, see, e.g., H. Waldock, ‘Third Report on the Law of Treaties’, 1964 YILC, Vol. II, at 55, para. 12; Report of the International Law Commission, UN Doc. A/60/10 (2005), 220, para. 479; I. Sinclair, The Vienna Convention on the Law of Treaties (1984), 124; R. Gardiner, Treaty Interpretation (2008), 64; M. Shaw, International Law (2008), 934; Brownlie, supra note 18, at 633. For references to the same principle in international jurisprudence, see notably Legal Consequences for States of the Continued Presence of South Africa in Namibia (South West Africa) notwithstanding Security Council Resolution 276 (1970), Advisory Opinion of 21 June 1971, [1971] ICJ Rep. 16, at 182 (Judge de Castro, Dissenting Opinion); Aegean Sea Continental Shelf (Greece v. Turkey), Judgment of 19 December 1978, [1978] ICJ Rep. 3, at 67 (Judge de Castro, Dissenting Opinion); Eritrea–Ethiopia Boundary Commission, Decision Regarding Delimitation of the Border between Eritrea and Ethiopia, Decision of 13 April 2002, RIAA, Vol. XXV, 83, at 110, para. 3.5.

24 Waldock, supra note 23.

25 Island of Palmas (Netherlands v. United States), Award of 4 April 1928, RIAA, Vol. II, 829, at 845; para. 16 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 222; Report of the International Law Commission, UN Doc. A/61/10 (2006), 415 (note 1025). See also para. 1 of the commentary to Art. 13 ARSIWA, Report of the International Law Commission, UN Doc. A/56/10, 57 (2001).

26 Jennings and Watts, supra note 18, at 1282; H. Thirlway, ‘The Law and Procedure of the International Court of Justice 1960–1989’, (2006) 77 BYIL 1, at 68.

27 Brownlie, supra note 18, at 633.

28 Gabcikovo-Nagymaros Project case, supra note 1, at 122, para. 8 (Judge Bedjaoui, Separate Opinion).

29 For basic support of the principle of contemporaneity in international jurisprudence, see generally Right of Nationals of the United States of America in Morocco (France v. United States of America), Judgment of 27 August 1952, [1952] ICJ Rep. 176, at 189; Minquiers and Ecrehos (France/United Kingdom), Judgment of 17 November 1953, [1953] ICJ Rep. 47, at 91 (Judge Levi Carneiro, Individual Opinion); South West Africa (Ethiopia v. South Africa; Liberia v. South Africa), supra note 3, at 23, paras. 16–17; Aegean Sea Continental Shelf case, supra note 23, at 63 (Judge de Castro, Dissenting Opinion); Gabcikovo-Nagymaros Project case, supra note 1; Kasikili/Sedudu Island (Botswana/Namibia), Judgment of 13 December 1999, [1999] ICJ Rep. 1045, at 1062, para. 25; ibid., at 1114, para. 4 (Judge Higgins, Declaration); Case Concerning the Land and Maritime Boundary between Cameroon and Nigeria (Equatorial Guinea intervening), Judgment of 10 October 2002, [2002] ICJ Rep. 303, at 346, para. 59; Eritrea–Ethiopia Boundary Commission Decision, supra note 23.

30 See Draft Art. 69(1)(b) and commentary thereto, YILC, supra note 23, at 199; Waldock, supra note 23, at 52 and 56, para. 15. See also Israel's proposal to include a separate rule on ‘inter-temporal linguistics’, YILC, supra note 18, at 95–6.

31 H. Waldock, ‘Sixth Report on the Law of Treaties’, YILC, supra note 18, at 96; para. 16 of the commentary to what became Art. 31 VCLT, ibid., 222.

32 1966 YILC, Vol. I (Part Two), at 199, para. 9.

33 See para. 16 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 222; Report of the International Law Commission, UN Doc. A/61/10 (2006), 415; Eritrea–Ethiopia Boundary Commission Decision, supra note 23. See also Award in the Arbitration Regarding the Iron Rhine Railway between the Kingdom of Belgium and the Kingdom of the Netherlands, supra note 18, at 72, para. 79; M. Fitzmaurice, ‘The Practical Working of the Law of Treaties’, in M. Evans (ed.), International Law (2006), 198–9.

34 Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23, at 31, para. 53.

35 Eritrea–Ethiopia Boundary Commission Decision, supra note 23.

36 Verbatim Record, 5 March 2009, CR 2009/4 (uncorrected), at 50, para. 4 (Mr Pellet on behalf of Nicaragua).

37 Judgment, supra note 5, paras. 14–15 (Judge ad hoc Guillaume, Declaration).

38 Report of the International Law Commission, UN Doc. A/60/10 (2005), 219, para. 474.

39 Aegean Sea Continental Shelf case, supra note 23, at 63 (Judge de Castro, Dissenting Opinion).

40 Gabcikovo-Nagymaros Project case, supra note 1, at 122, para. 7(iii) (Judge Bedjaoui, Separate Opinion) (emphasis in original).

41 Kasikili/Sedudu Island (Botswana/Namibia), supra note 29, at 1114, para. 4 (Judge Higgins, Declaration).

42 Jennings and Watts, supra note 18, at 1282.

43 Judgment, supra note 5, paras. 4–7 (Judge Skotnikov, Separate Opinion); ibid., paras. 15–16 (Judge ad hoc Guillaume, Declaration).

44 Judgment, supra note 5, para. 58.

45 Nicaragua Rejoinder, paras. 1.10 and 3.99 (hereinafter NCR).

46 NCM, supra note 21, para. 4.3.9; Judgment, supra note 5, para. 58.

47 NCM, supra note 21, para. 4.3.9; NCR, supra note 45, para. 3.90.

48 NCM, supra note 21, para. 4.3.9.

49 Judgment, supra note 5, para. 59.

50 CRM, supra note 12, para. 4.60.

51 See, e.g., CRM, supra note 12, para. 4.59; NCM, supra note 21, para. 1.3.15.

52 Verbatim Record, supra note 12, at 15, para. 28 (Mr Crawford on behalf of Costa Rica).

53 Costa Rica Reply, para. 2.52.

54 Judgment, supra note 5, paras. 63–64.

55 Judgment, supra note 5, para. 4 (Judge Skotnikov, Separate Opinion).

56 Ibid., para. 16 (Judge ad hoc Guillaume, Declaration).

57 Ibid. See also ibid., para. 10 (Judge Skotnikov, Separate Opinion).

58 For the debate on first reading, see 1964 YILC, Vol. I, at 33–9.

59 YILC, supra note 18, at 222, para. 16.

60 Ibid..

61 Island of Palmas (Netherlands v. United States), supra note 25.

62 YILC, supra note 58, at 33, para. 6 (Mr Verdross); Gabcikovo-Nagymaros Project case, supra note 1, at 122 (Judge Bedjaoui, Separate Opinion).

63 Gabcikovo-Nagymaros Project case, supra note 1, at 124, para. 18; NCM, supra note 21, para. 4.3.18.

64 YILC, supra note 58, at 34, para. 10.

65 See para. 16 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 222.

66 Ibid..

67 It is generally agreed that the term ‘good faith’ in Art. 31(1) VCLT is largely an indirect reference to the principle of effective interpretation (ut res magis valeat quam pereat). See para. 6 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 219. For a more recent discussion, see R. Gardiner, Treaty Interpretation (2008), 147–61; M. Villiger, Commentary on the 1969 Vienna Convention on the Law of Treaties (2009), 425–6; J.-M. Sorel, ‘Article 31: Convention de 1969’, in O. Corten and P. Klein (eds.), Les conventions de Vienne sur le droit des traités: Commentaire article par article, Vol. II (2006), 1309.

68 Maritime Delimitation and Territorial Questions between Qatar and Bahrain (Qatar v. Bahrain), Jurisdiction and Admissibility, Judgment of 15 February 1995, [1995] ICJ Rep. 6, at 39 (Judge Schwebel, Dissenting Opinion).

69 For a similar conclusion, see A. Orakhelashvili, The Interpretation of Acts and Rules in Public International Law (2008), 291.

70 Verbatim Record, supra note 36, at 49, para. 3 (Mr Pellet on behalf of Nicaragua) (‘le principe de base qui constitue la toile de fond de cette opération n'a rien de mystérieux et me paraît vraiment indiscutable; il est celui-là même qui inspire le droit des traités dans son ensemble: tout se rapporte à l'intention des Parties’) (emphasis in original).

71 See para. 4 of the Wiesbaden resolution entitled ‘The Intertemporal Problem in Public International Law’, adopted by the Institut de droit international on 11 August 1975, available at www.idi-iil.org.

72 See paras. 8–9 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 219–20. More recently, an ICSID tribunal has aptly described this as a ‘process of progressive encirclement’; see Aguas del Tunari v. Bolivia (ICSID ARB/02/03), Award of 21 October 2005, para. 91.

73 See para. 4 of the commentary to what became Art. 31 VCLT, YILC, supra note 18, at 218; Waldock, supra note 23, at 54, para. 6.

74 Compare J. Crawford, ‘Second Report on State Responsibility’, 1999 YILC, Vol. II (Part One), at 18, para. 43.

75 McNair, supra note 18, at 364.

76 Fitzmaurice, M., ‘Dynamic (Evolutive) Interpretation of Treaties: Part I’, (2008) 21 Hague Yearbook of International Law 101Google Scholar, at 102.

77 For the various situations in which international jurisprudence has relied on the principle of evolutionary interpretation, see notably Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23, at 31, para. 53 (relying on the contemporary law of self-determination to give effect to Art. 22 of the League Covenant in accordance with Art. 31(3)(c) VCLT); Tyrer v. United Kingdom, European Court of Human Rights, Application No. 5856/72, Judgment of 25 April 1978, para. 31 (relying on an evolutionary interpretation in order to ensure an application of the European Convention on Human Rights and Fundamental Freedoms that would be effective in terms of its object and purpose, holding in a classic statement that the Convention is ‘a living instrument . . . which must be interpreted in the light of present-day conditions’); Aegean Sea Continental Shelf case, supra note 23, at 32, para. 77; Interpretation of the American Declaration on the Rights and Duties of Man within the Framework of Article 64 of the American Convention on Human Rights, Inter-American Court of Human Rights, Advisory Opinion OC-10/89 of 14 July 1989, para. 37 (citing the ICJ in Namibia to the effect that ‘an international instrument must be interpreted and applied within the overall framework of the juridical system in force at the time of the interpretation’); Gabcikovo-Nagymaros Project case, supra note 1, at 67–8, para. 112 (newly developed norms of environmental law relevant to the implementation of a 1977 Treaty in accordance with Art. 31(3)(c) VCLT); Roger Judge v. Canada, UN Human Rights Committee, Communication No. 829/1998, paras. 10.3–10.4 (referring to the International Covenant on Civil and Political Rights as a ‘living instrument’ on the basis of Art. 31(1) VCLT); Award in the Arbitration Regarding the Iron Rhine Railway between the Kingdom of Belgium and the Kingdom of the Netherlands, supra note 18, at 72–4, paras. 79–81 (relying on an evolutionary interpretation in order to ensure an application of a 1839 Treaty of Separation that would be effective in terms of its object and purpose).

78 Judgment, supra note 5, para. 10 (Judge ad hoc Guillaume, Declaration) (and see ibid., paras. 11–12 for references to the case law).

79 See South West Africa (Ethiopia v. South Africa; Liberia v. South Africa), supra note 3, at 23, paras. 16–17; Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23, at 31, para. 53.

80 For the purposes of this article, it will not be necessary to consider the Court's reliance on the doctrine of evolutionary interpretation in the Gabcikovo-Nagymaros Project case, supra note 1, at 67 and 77–8, paras. 112 and 140.

81 Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23.

82 Ibid., para. 45.

83 Ibid., para. 53.

84 Ibid., para. 54.

85 In this case, the French–Mexican Claims Commission stressed that a treaty must tacitly be seen as referring to general international law ‘for all questions which it does not itself resolve expressly and in a different way’. See Georges Pinson (France v. United Mexican States), Award of 13 April 1928, RIAA, Vol. V, 422.

86 Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23, at 31, para. 53.

87 See Thirlway, supra note 26, at 136–7.

88 Legal Consequences for States of the Continued Presence of South Africa in Namibia case, supra note 23, at 277, para. 85 (Judge Fitzmaurice, Dissenting Opinion).

89 Ibid., at 28, para. 45.

90 For a contemporaneous reference to the peremptory status of the principle of self-determination, see para. 3 of the commentary to what became Art. 53 VCLT, YILC, supra note 18, at 248. For a similar argument, see Orakhelashvili, supra note 69, at 377 (note 300). For recognition by the Court of the potential role of Art. 64 VCLT see, e.g., Gabcikovo-Nagymaros Project case, supra note 1, at 67, para. 112.

91 Gabcikovo-Nagymaros Project case, supra note 1, at 122, paras. 9–10.

92 Aegean Sea Continental Shelf case, supra note 23.

93 Ibid., at 33, para. 78.

94 Ibid., at 33, para. 78.

95 Ibid., at 21, para. 48.

96 Ibid., at 29, para. 70.

97 Ibid., at 30, para. 72.

98 Ibid., at 30, para. 73 (emphasis in original).

99 Ibid., at 31, para. 74.

100 Ibid., at 32, para. 77.

101 Ibid., at 32, para. 77.

102 Ibid., at 34–7, paras. 81–90.

103 Ibid., at 62–3 (Judge de Castro, Dissenting Opinion).

104 See Thirlway, supra note 26, at 142.

105 For a similar conclusion, see Aegean Sea Continental Shelf case, supra note 23, at 64–5; and implicitly Thirlway, supra note 26, at 142.

106 Aegean Sea Continental Shelf case, supra note 23, at 33, para. 79.

107 For a similar conclusion, see Thirlway, supra note 26, at 143 (noting that the Court's requirement was ‘hardly appropriate’).

108 Aegean Sea Continental Shelf case, supra note 23, at 65 (Judge de Castro, Dissenting Opinion).

109 Kasikili/Sedudu Island (Botswana/Namibia), supra note 29, at 1113–14, para. 2 (Judge Higgins, Declaration).

110 Aegean Sea Continental Shelf case, supra note 23, at 63–4.

111 See Interpretation of Peace Treaties with Bulgaria, Hungary and Romania, Second Phase, Advisory Opinion of 18 July 1950, [1950] ICJ Rep. 229.

112 Gabcikovo-Nagymaros Project case, supra note 1, at 77–8.

113 Ibid., at 121–2 (Judge Bedjaoui, Separate Opinion) (emphasis in original). In the passage quoted above, Judge Bedjaoui relied in part on M. K. Yasseen, ‘L'interprétation des traités d'après la Convention de Vienne sur le droit des traités’, 151 RdC (1976) 1, at 64.

114 NCR, supra note 45, para. 2.56; Verbatim Record, supra note 36, at 50, para. 4 (Mr Pellet on behalf of Nicaragua).

115 NCR, supra note 45, para. 3.98; Verbatim Record, supra note 36, at 50, para. 5 (Mr Pellet on behalf of Nicaragua).

116 Verbatim Record, supra note 36, at 50, para. 5 (Mr Pellet on behalf of Nicaragua).

117 Ibid., at 35, paras. 57–59 (Mr Kohen on behalf of Costa Rica).

118 Judgment, supra note 5, paras. 66–67.

119 Ibid., para. 68.

120 Ibid., paras. 70–71.

121 Ibid., para. 5 (Judge Skotnikov, Separate Opinion).

122 Ibid., para. 6.

123 Ibid., paras. 8–10.

124 Case of Certain Norwegian Loans (France v. Norway), Judgment of 6 July 1957, [1957] ICJ Rep. 9, at 25.