¹ Military and Paramilitary Activities in and against Nicaragua (Nicaragua v United States of America) (Merits) [1986] I.C.J. Rep. 14.

² Custom is a classic topic extensively explored even before Nicaragua. For example, see Parry, C., The Sources and Evidences of International Law (Manchester 1965), 56–82Google Scholar; D'Amato, A., The Concept of Custom in International Law (Ithaca 1971)Google Scholar; Akehurst, M., “Custom as a Source of International Law” (1975) 47 B.Y.I.L. 1Google Scholar.

³ North Sea Continental Shelf (Federal Republic of Germany/Denmark; Federal Republic of Germany/Netherlands) (Merits) [1969] I.C.J. Rep. 3, at [77].

⁴ Military and Paramilitary Activities, at [183]–[209]. See also Kirgis, F., “Custom on a Sliding Scale” (1987) 81 A.J.I.L. 146Google Scholar; D'Amato, A., “Trashing Customary International Law” (1987) 81 A.J.I.L. 101Google Scholar.

⁵ Roberts, A., “Traditional and Modern Approaches to Customary International Law: A Reconciliation” (2001) 95 A.J.I.L. 757Google Scholar; Alvarez-Jiménez, A., “Methods for the Identification of Customary International Law in the International Court of Justice's Jurisprudence: 2000–2009” (2011) 60 I.C.L.Q. 681Google Scholar.

⁶ Report of the International Law Commission, UN Doc A/66/10 (3 October 2011), 305–06, at [1]–[5] (Annex A).

⁷ First Report, UN Doc A/CN.4/663 (17 May 2013); Second Report, UN Doc A/CN.4/672 (22 May 2014); Third Report, UN Doc A/CN.4/682 (27 March 2015); Fourth Report, UN Doc A/CN.4/695 (8 March 2016); Fifth Report, UN Doc A/CN.4/717 (14 March 2018).

⁸ Draft Conclusions on Identification of Customary International Law with Commentaries, UN Doc A/73/10 (17 August 2018), 119–56.

⁹ UN Doc A/RES/73/203 (20 December 2018).

¹⁰ Report of the International Law Commission, UN Doc A/67/10 (7 September 2012), 109, at [171].

¹¹ Ibid., at [169].

¹² Report of the International Law Commission, UN Doc A/69/10 (14 August 2014), 242, at [158].

¹³ Second Report, at [28]. See also Draft Conclusions, 126.

¹⁴ E.g. see Petersen, N., “The International Court of Justice and the Judicial Politics of Identifying Customary International Law” (2017) 28 E.J.I.L. 357Google Scholar; Joyner, D., “Why I Stopped Believing in Customary International Law” (2019) 9 Asian J.I.L. 31Google Scholar.

¹⁵ Talmon, S., “Determining Customary International Law: The ICJ's Methodology Between Induction, Deduction and Assertion” (2015) 26 E.J.I.L. 417, 419Google Scholar and especially 434–40. Talmon's remarks might apply to custom identification by the ILC, as explained in a 2013 Secretariat Memorandum. See UN Doc A/CN.4/659 (14 March 2013), at [14]–[15].

¹⁶ This was the case for the ICJ's judgment in Jurisdictional Immunities of the State (Germany v Italy; Greece intervening) (Judgment) [2012] I.C.J. Rep. 99. See Wuerth, I., “International Law in Domestic Courts and the Jurisdictional Immunities of the State Case” (2012) 13 Melbourne J.I.L. 813Google Scholar; Dickinson, A., “Germany v. Italy and the Territorial Tort Exception: Walking the Tightrope” (2013) 11 J.I.C.J. 147Google Scholar.

¹⁷ Section V(C) below.

¹⁸ Helmersen, S.T., The Application of Teachings by the International Court of Justice (Cambridge 2021), 47CrossRefGoogle Scholar.

¹⁹ P. Tomka, “Custom and the International Court of Justice” (2013) 12 L.P.I.C.T. 195, 202. Nicholson made a similar point when discussing the judgment in Factory at Chórzow. See Nicholson, R., “The International Court of Justice as a ‘Shortcut’ to Identifying Custom” (2021) 12 L.P.I.C.T. 490, 497Google Scholar.

²⁰ Studies on judicial deliberations have focused primarily on domestic courts. See H.T. Edwards, “The Effects of Collegiality on Judicial Decision Making” (2003) 151 U. Pa. L. Rev. 1639, 1643; Komárek, J., “Questioning Judicial Deliberations” (2009) 29 O.J.L.S. 805Google Scholar; Cohen, M., “Ex Ante Versus Ex Post Deliberations: Two Models of Judicial Deliberations in Courts of Last Resort” (2014) 62 A.J.C.L. 951Google Scholar.

²¹ Hernández wrote that “[s]ubstantial airing of individual views occurs at several stages throughout the [deliberation] process”. See Hernández, G.I., The International Court of Justice and the Judicial Function (Oxford 2014), 106–07CrossRefGoogle Scholar.

²² Section III below.

²³ Statute of the International Court of Justice, art. 36. See also ibid., art. 38.

²⁴ Sender and Wood have written that “assertion is self-evidently not a methodology for determining the existence of a rule of customary international law [but] essentially a way of drafting a judgment”, O. Sender and M. Wood, “The International Court of Justice and Customary International Law: A Reply to Stefan Talmon” EJIL:Talk!, 30 November 2015, available at https://www.ejiltalk.org/the-international-court-of-justice-and-customary-international-law-a-reply-to-stefan-talmon/ (last accessed 8 June 2022).

²⁵ Section V(C) below.

²⁶ Sir Hersch Lauterpacht wrote that the work of individual judges in deliberations “may bear the impress of unity associated with the intellectual effort of a single individual”, Lauterpacht, H., The Development of International Law by the International Court (Cambridge 1982), 63Google Scholar.

²⁷ Section IV(B) below.

²⁸ Thirlway held the opposite view. See H. Thirlway, “The Drafting of ICJ Decisions: Some Personal Recollections and Observations” (2006) 5 Chinese J.I.L. 15, 16.

²⁹ Besides Thirlway, see Hernández, The International Court, 95–125; A. Gros, “Observations sur le Mode de Délibération de la Cour internationale de Justice” (1975) 14 Comunicazioni e Studi 377; R.B. Lillich and G.E. White, “The Deliberative Process of the International Court of Justice: A Preliminary Critique and Some Possible Reforms” (1976) 70 A.J.I.L. 28; R. Jennings, “The Drafting of ICJ Decisions: Some Personal Recollections and Observations” (1988) 59 B.Y.I.L. 31; Jennings, R., “The Collegiate Responsibility and Authority of the International Court of Justice” in Dinstein, Y. (ed.), International Law at a Time of Perplexity: Essays in Honour of Shabtai Rosenne (Dordrecht 1989), 343Google Scholar; M. Shaw, Rosenne's Law and Practice of the International Court 1920–2015, 2nd ed., vol. 3 (Leiden 2015), 1567–75; B. Fassbender, “Article 54” in A. Zimmermann and C.J. Tams (eds.), The Statute of the International Court of Justice: A Commentary, 3rd ed. (Oxford 2019), 1499, 1500–02.

³⁰ Resolution concerning the Internal Judicial Practice of the Court, art. 10.

³¹ Ibid., art. 1.

³² Thirlway, “The Drafting”, 16.

³³ Hernández, The International Court, 104.

³⁴ Thirlway, “The Drafting”, 16.

³⁵ Resolution, art. 2, to which Article 3(i) refers.

³⁶ Ibid., art. 4. The established practice is for this note to be written in all deliberations on the merits.

³⁷ Jennings, “The Drafting”, 39.

³⁸ Thirlway, “The Drafting”, 17.

³⁹ Resolution, art. 5.

⁴⁰ Ibid., art. 6(i).

⁴¹ Ibid., art. 6(ii).

⁴² Lillich and White, “The Deliberative Process”, 36.

⁴³ Hernández, The International Court, 107.

⁴⁴ Buergenthal, T., “Rosalyn Higgins: Judge and President of the International Court of Justice (1995–2009)” (2009) 22 L.J.I.L. 703, 712Google Scholar.

⁴⁵ Wiles, N., “The International Court of Justice” in Baetens, F. (ed.), Legitimacy of Unseen Actors in International Adjudication (Cambridge 2019), 31, 36Google Scholar.

⁴⁶ Resolution, art. 7(i).

⁴⁷ Ibid., art. 7(iii).

⁴⁸ Ibid., art. 7(ii).

⁴⁹ Ibid., art. 8(i), (v).

⁵⁰ Ibid., art. 7(iv).

⁵¹ See Shahabuddeen, M., Precedent in the World Court (Cambridge 1996), 128CrossRefGoogle Scholar.

⁵² Respondents were asked: “Would you agree that parties before the Court endeavour to structure their submissions also according to the Court's expectation of how a case should be pleaded?” Ten replied “Yes”, three replied “Neither yes or no”.

⁵³ Respondents were asked: “Does the President's List of Issues presented before the Article 3 deliberation tend to follow the structure of the parties’ submissions?” Seven replied “Neither yes or no”, four replied “Yes” and two replied “No”. Two of the five respondents who made additional comments emphasised the link between the List of Issues and the pleadings.

⁵⁴ 499 UNTS 311.

⁵⁵ North Sea Continental Shelf, at [75]–[80].

⁵⁶ Jurisdictional Immunities of the State, at [62]–[106].

⁵⁷ For North Sea Continental Shelf, see Memorial of the Federal Republic of Germany (21 August 1967), at [54]–[62]; Counter-memorial of Denmark (20 February 1968), at [84]–[112]; Counter-memorial of the Netherlands (20 February 1968), at [78]–[106]; Reply of the Federal Republic of Germany (31 May 1968), at [32]–[55]; Common Rejoinder of Denmark and the Netherlands (30 August 1968), at [54]–[75]. For Jurisdictional Immunities of the State, see Memorial of Germany (12 June 2009), at [47]–[133]; Counter-memorial of Italy (22 December 2009), at [4.12]–[4.42], [4.56]–[4.77]; Reply of Germany (5 October 2010), at [37]–[66]; Rejoinder of Italy (10 January 2011), at [4.1]–[4.23].

⁵⁸ Legal Consequences of the Separation of the Chagos Archipelago from Mauritius in 1965 (Advisory Opinion) [2019] I.C.J. Rep. 95. See Section IV(C)(1) below.

⁵⁹ Respondents were asked: “How much influence do you perceive the parties’ submissions concerning custom identification to have on the Court's choice of how to record its custom identification exercise in a judgment or advisory opinion?” Eight replied “Some influence”, four replied “Considerable influence” and one replied “Determinative influence”. The additional comments indicate that some respondents have replied “Some influence” because, although the Court is responsive to the parties’ arguments, it retains the final say on the framing of the identification exercise.

⁶⁰ Section IV(C)(1) below. Beyond being a possible basis for asserting the existence of customary rules, reliance on General Assembly resolutions can also fit into custom identification by induction, where resolutions are seen to convey the opinio juris of states, or deduction, where resolutions are the basis on which to infer the existence of customary rules.

⁶¹ Memorial of Nicaragua (30 April 1985), at [437]–[497].

⁶² Respondents were asked: “Do you think it is more or less likely for the Court to record custom identification as an analysis of State practice and opinio juris if both parties structure their submissions on custom identification as an analysis of evidence of State practice and opinio juris?” Eight replied “More likely” and five replied “Neither more likely or less likely”. Respondents were also asked: “Do you think it is more or less likely for the Court to record custom identification as an analysis of State practice and opinio juris if neither party structures its submissions on custom identification as an analysis of evidence of State practice and opinio juris?” Seven replied “Less likely” and six replied “Neither more likely or less likely”.

⁶³ Respondents were asked: “In your view, is the Court's approach to custom identification in a judgment or advisory opinion influenced by the analytical approach to custom identification of the individuals acting in the early stages of the deliberation process up to and excluding the election of the drafting committee at the close of the Article 5 deliberation (i.e., President, Judges writing individual notes for the Article 5 deliberation, and Registry officials assigned to a case)?” Eight replied “Yes” and five replied “Neither yes or no”.

⁶⁴ This active role of the court would be in application of the principle iura novit curia. See Thirlway, H., The International Court of Justice (Oxford 2016), 32–33Google Scholar.

⁶⁵ Jurisdictional Immunities of the State, at [72].

⁶⁶ Respondents were asked: “In your view, does the familiarity of these individuals [i.e. President, Judges writing individual notes for the Article 5 deliberation, and Registry officials assigned to a case] with the content of the customary rule to be ascertained make it more or less likely that the final judgment or advisory opinion will record custom identification as an analysis of evidence of State practice and opinio juris?” Seven replied “Neither more likely or less likely”, five replied “More likely” and one replied “Less likely”.

⁶⁷ Respondents were asked: “Imagine a situation in which a custom identification methodology is chosen in the early stages of the deliberation process and is shown in the preliminary draft judgment or advisory opinion. Imagine that certain judges who receive the preliminary draft favour a different custom identification methodology, but the methodology recorded in the preliminary draft results in the outcome that these judges desire. In your view, is it more or less likely for these judges to disagree with the methodology proposed in the preliminary draft, given that this methodology results in their desired outcome?” Seven replied “Less likely”, four replied “Neither more likely or less likely” and two replied “More likely”.

⁶⁸ M.J. Aznar and E. Methymaki, “Article 3” in Zimmermann and Tams (eds.), The Statute of the International Court of Justice, 289, 303–05. Former national judges commonly sit on the European Court of Human Rights and Inter-American Court of Human Rights, but they are also known to be members of ITLOS. The WTO Appellate Body is mainly composed of former government lawyers and legal academics, with the latter being well-represented also on ITLOS.

⁶⁹ As of July 2022, the court is composed of four legal academics (Judges Bennouna, Iwasawa, Nolte and Charlesworth), three career diplomats (Judges Tomka, Gevorgian and Salam), three national judges (Judges Abraham, Sebutinde and Bhandari) and four officials of governments and international organisations (President Donoghue and Judges Yusuf, Xue and Robinson). Several judges have worked in more than one capacity: for example, Judge Abraham was also a Foreign Ministry official and an academic, Judge Bennouna was also Morocco's ambassador to the UN and Judge Salam was also an academic.

⁷⁰ Respondents were asked: “In your view, does the professional background of judges before becoming members of the Court influence their degree of familiarity with custom identification methodologies?” Eleven replied “Yes”, one replied “No” and one replied “Neither yes or no”.

⁷¹ McKenzie, R., “The Selection of International Judges” in Romano, C.P.R., Alter, K.J. and Shany, Y. (eds.), The Oxford Handbook of International Adjudication (Oxford 2014), 737, 740–42Google Scholar.

⁷² First Report, at [84].

⁷³ Respondents were asked: “In your view, do judges not familiar with custom identification methodologies find identifying customary international law by induction based on evidence of State practice and opinio juris more cumbersome than doing so by non-inductive methodologies (e.g., relying on the parties’ agreement, General Assembly resolutions, and earlier judicial decisions)?” Seven replied “Yes” and six replied “Neither yes or no”.

⁷⁴ Respondents were asked: “Imagine a situation in which members of a drafting committee have different views on the appropriate manner to record a custom identification exercise in the draft judgment or advisory opinion. In your view, is it more or less likely that, in such a situation, the compromise between the judges’ different views would be to record custom identification as induction based on evidence of State practice or opinio juris?” Nine replied “Neither more likely or less likely”, three replied “More likely” and one replied “Less likely”.

⁷⁵ Wood, M., “Method and Style in International Law, and the International Court of Justice's Contribution” in Teles, P. Galvão and Ribeiro, M. Almeida (eds.), Case-law and the Development of International Law: Contributions by International Courts and Tribunals (Leiden 2021), 14, 27Google Scholar.

⁷⁶ Respondents were asked: “In your view, does collegiality in the Court's deliberation process promote recording custom identification by shorter, non-inductive reasoning (including, for example, by relying on the parties’ agreement, General Assembly resolutions, and earlier judicial decisions)?” Ten replied “Yes”, one replied “No” and two replied “Neither yes or no”.

⁷⁷ Thirlway, The International Court, 126.

⁷⁸ For example, see Cassese, A., “The Nicaragua and Tadic Tests Revisited in Light of the ICJ Judgment on Genocide in Bosnia” (2007) 18 E.J.I.L. 649, 651Google Scholar; Scobbie, I., “‘Une hérésie en matière judiciaire’? The Role of the Judge ad hoc in the International Court” (2005) 4 L.P.I.C.T. 421Google Scholar.

⁷⁹ 1833 UNTS 3.

⁸⁰ Territorial and Maritime Dispute (Nicaragua v Colombia) (Merits) [2012] I.C.J. Rep. 624, at [118].

⁸¹ Baumaert, K.A., “The Outer Limits of the Continental Shelf under Customary International Law” (2017) 111 A.J.I.L. 827, 836–37Google Scholar.

⁸² Hernández, The International Court, 108.

⁸³ Respondents were asked: “In your view, does the concern for agreement typical of the Court's collective drafting process push judges to identify a common position expressed in a judicial decision that maximises the number of supportive votes?” Eleven replied “Yes” and two replied “Neither yes or no”.

⁸⁴ Respondents were asked: “In your experience, does the text of a preliminary draft judgment or advisory opinion change considerably during the deliberation process?” Ten replied “Yes”, two replied “No” and one replied “Neither yes or no”.

⁸⁵ Legal Consequences of the Separation, at [144]–[162].

⁸⁶ Judge Donoghue dissented for reasons other than whether the right to self-determination was part of customary international law.

⁸⁷ Written Statement of the US, at [4.23]–[4.72]; CR 2018/24, 16–19, at [42]–[55] (US).

⁸⁸ CR 2018/21, 45–51, at [12]–[30] (UK).

⁸⁹ Written Comments of Mauritius, at [3.23]–[3.41]; Written Comments of Nicaragua, at [5]–[9]; CR 2018/25, 27–29, at [19]–[32] (Kenya); CR 2018/20, 45–49, at [5]–[17] (Mauritius).

⁹⁰ Written Statement of the African Union, at [67]–[106]; Written Statement of Belize, at [2.1]–[2.22]; Written Comments of Cyprus, at [17]–[18]; Written Statement of the Netherlands, at [3.4]–[3.8]; CR 2018/23, 9–10, at [7]–[13] (Belize); CR 2018/26, 30–36, at [10]–[31] (Vanuatu).

⁹¹ CR 2018/23, 36–37, at [23]–[26] (Botswana).

⁹² Written Statement of Brazil, at [18].

⁹³ Respondents were asked: “In your view, when parties to a case or participant States in advisory proceedings make submissions on custom identification using different custom identification methodologies, is it likely or not that different judges within the Court would similarly take different approaches to custom identification in their individual work (e.g., notes for the Article 5 deliberation and individual opinions), perhaps influenced by the submissions of a particular party or participant State?” Seven replied “Likely”, five replied “Somewhat likely” and one replied “Not likely”.

⁹⁴ Respondents were asked: “Imagine a case or advisory proceedings in which the Court's decision depends on the existence of a rule of customary international law. In your view, if, in such a case or advisory proceedings, the Court does not record its custom identification exercise by induction based on evidence of State practice and opinio juris, is it likely because judges could not agree on induction being the most appropriate methodology to show record the custom identification exercise?” Seven replied “Somewhat likely” and six replied “Not likely”.

⁹⁵ Respondents were asked: “In your view, does collegiality in the Court's deliberation process promote reducing reasoning only to what is necessary to decide a case?” Nine replied “Yes” and four replied “Neither yes or no”.

⁹⁶ Application of the Convention on the Prevention and Punishment of the Crime of Genocide (Bosnia and Herzegovina v Serbia and Montenegro) (Merits) [2007] I.C.J. Rep. 43, at [385], [401], [420]; Gabčikovo-Nagymaros Project (Hungary/Slovakia) (Judgment) [1997] I.C.J. Rep. 7, at [51]–[52].

⁹⁷ Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory (Advisory Opinion) [2004] I.C.J. Rep. 136, at [140]; Maritime Dispute (Peru v Chile) (Judgment) [2014] I.C.J. Rep. 3, at [179]; Oil Platforms (Islamic Republic of Iran v United States of America) (Merits) [2003] I.C.J. Rep. 161, at [74], [76].

⁹⁸ Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) (Judgment) [2005] I.C.J. Rep. 168, at [162]; Questions relating to the Obligation to Prosecute or Extradite (Belgium v Senegal) (Judgment) [2012] I.C.J. Rep. 422, at [99].

⁹⁹ Obligation to Negotiate Access to the Pacific Ocean (Bolivia v Chile) (Merits) [2018] I.C.J. Rep. 507, at [116]; Certain Questions of Mutual Assistance in Criminal Matters (Djibouti v France) (Judgment) [2008] I.C.J. Rep. 177, at [124]; Territorial Dispute (Libya/Chad) (Judgment) [1994] I.C.J. Rep. 6, at [41].

¹⁰⁰ Nicaragua v Colombia, at [118].

¹⁰¹ Legal Consequences of the Separation, at [144]–[162].

¹⁰² Nicaragua v Colombia, at [113]–[131].

¹⁰³ Hernández, The International Court, 109.

¹⁰⁴ Section V(C) below.

¹⁰⁵ Talmon, “Determining”, 437.

¹⁰⁶ For example, see Draft Articles on Responsibility of States for Internationally Wrongful Acts with Commentaries, UN Doc A/56/10 (1 October 2001), 287, at [3]; Draft Articles on the Responsibility of International Organizations with Commentaries, UN Doc A/66/10 (3 October 2001), 70, at [5]. Certain ILC proposals start as progressive development, only finally to be regarded as codification. For example, see the comments on Article 16 of the Draft Articles on State Responsibility in J. Crawford, State Responsibility: The General Part (Cambridge 2013), 401 (footnote 28).

¹⁰⁷ Draft Conclusions, 129.

¹⁰⁸ Ibid.

¹⁰⁹ Ibid.

¹¹⁰ Ibid.

¹¹¹ Talmon, “Determining”, 423, 442.

¹¹² Choi, S.J. and Gulati, M., “Customary International Law: How do Courts do it?” in Bradley, C. (ed.), Custom's Future: International Law in a Changing World (Cambridge 2016), 117, 129Google Scholar.

¹¹³ Petersen, “The International Court”, 372. In Nicaragua, the Court stated that the parties’ agreement “does not […] dispense [it] from having itself to ascertain what rules of customary international law are applicable”, Military and Paramilitary Activities, at [184]. The Court has not always lived up to this statement. See Nicaragua v Colombia, at [116]–[118].

¹¹⁴ Statute of the International Court of Justice, art. 59.

¹¹⁵ Interpretation of Peace Treaties with Bulgaria, Hungary and Romania (First Phase) [1950] I.C.J. Rep. 65, 71.

¹¹⁶ Military and Paramilitary Activities, at [183]–[209].

¹¹⁷ Ibid., at 156–57 (Separate Opinion Nagendra Singh); ibid., at 199 (Separate Opinion Sette-Camara).

¹¹⁸ Djibouti v France, at [174].

¹¹⁹ Ibid., at [37] (Separate Opinion Yusuf).

¹²⁰ Nicaragua v Colombia, at [118].

¹²¹ Ibid., at [3] (Separate Opinion Abraham); ibid., at [3] (Declaration Mensah). For another example of asserting the existence of custom where the Court has also done so, see Arrest Warrant of 11 April 2000 (Democratic Republic of the Congo v Belgium) (Judgment) [2002] I.C.J. Rep. 3, at [14] (Dissenting Opinion Oda).

¹²² Jurisdictional Immunities of the State, at [6] (Separate Opinion Koroma).

¹²³ Right of Passage over Indian Territory (Portugal v India) (Merits) [1960] I.C.J. Rep. 6, 22.

¹²⁴ Ibid., at 39–43.

¹²⁵ Ibid., at [1]–[17] (Separate Opinion Wellington Koo).

¹²⁶ Legal Consequences of the Separation, at [144]–[162].

¹²⁷ Ibid., at [5]–[13] (Separate Opinion Sebutinde); ibid., at [3]–[47] (Separate Opinion Robinson).

¹²⁸ Respondents were asked: “Imagine a situation in which the Court positively identifies the existence of a rule of customary international law (by whichever methodology). Imagine that one or more judges, while agreeing with the Court's decision, write an individual opinion in which they record their own custom identification exercise by induction based on evidence of State practice and opinio juris. In your view, is it likely that, in thus recording their own custom identification exercise, these judges may wish to provide the Court's reasoning with further support?” Eight replied “Likely”, four replied “Somewhat likely” and one replied “Very likely”.

¹²⁹ Right of Passage, at 88–96 (Separate Opinion Moreno Quintana); ibid., at 97–115 (Separate Opinion Spender).

¹³⁰ Arrest Warrant, at [11]–[23] (Dissenting Opinion Van den Wyngaert). See also Military and Paramilitary Activities, at [94]–[98] (Dissenting Opinion Schwebel); ibid., at 531 (Dissenting Opinion Jennings); Jurisdictional Immunities of the State, at [21]–[27] (Dissenting Opinion Yusuf); ibid at [1]–[12] (Dissenting Opinion Gaja).

¹³¹ Dispute regarding Navigational and Related Rights (Costa Rica v Nicaragua) (Judgment) [2009] I.C.J. Rep. 213, at [22]–[28] (Separate Opinion Sepúlveda-Amor).

¹³² Certain Activities Carried Out by Nicaragua in the Border Area (Costa Rica v Nicaragua); Construction of a Road in Costa Rica along the San Juan River (Nicaragua v Costa Rica) (Judgment) [2015] I.C.J. Rep. 665, at [13] (Separate Opinion Donoghue). See also Military and Paramilitary Activities, at [7] (Separate Opinion Ago).

¹³³ Arrest Warrant, at [45]–[46].

¹³⁴ Ibid., at [12] (Separate Opinion Guillaume); ibid., at [20]–[45] (Joint Separate Opinion Higgins, Kooijmans and Buergenthal).

¹³⁵ Belgium v Senegal, at [55].

¹³⁶ Ibid., at [30]–[32] (Separate Opinion Abraham).

¹³⁷ See D.H. Anderson, “Deliberations, Judgments and Separate Opinions in the Practice of the International Tribunal for the Law of the Sea” in M.H. Nordquist and J.N. Moore (eds.), Current Marine Environmental Issues and the International Tribunal for the Law of the Sea (Leiden 2001), 63. On the WTO, see Dispute Settlement Understanding, 1869 UNTS 401; Working Procedures for Appellate Review, Doc WT/AB/WP/6 (16 August 2010). See also van den Bossche, P. and Zdouc, W., The Law and Policy of the World Trade Organization, 4th ed. (Cambridge 2018), 283–84Google Scholar.

¹³⁸ For example, judge rapporteurs prepare notes suggesting developments in the jurisprudence and, in deliberations, speak before other judges, who suggest amendments to the judge rapporteurs’ drafts only if necessary. See H. Keller and C. Heri, “Deliberation and Drafting: European Court of Human Rights (ECtHR)” in Max Planck Encyclopaedia of Public International Law, at [27], [38], available at https://opil.ouplaw.com/view/10.1093/law-mpeipro/e3210.013.3210/law-mpeipro-e3210?rskey=Us2Vag&result=2&prd=MPIL (last accessed 8 June 2022); Pasqualucci, J.M., The Practice and Procedure of the Inter-American Court of Human Rights, 2nd ed. (Cambridge 2012), 178–79CrossRefGoogle Scholar.

¹³⁹ On 31 December 2019, about 59,800 applications were pending before the ECtHR. The IACtHR has heard 402 contentious cases and 26 advisory ones since 1979.

¹⁴⁰ On 31 December 2019, 1,102 cases were pending at the Court of Justice and 1,398 cases at the General Court.

¹⁴¹ Rules of Procedure of the Court of Justice, arts. 15–16, 59, 197; Rules of Procedure of the General Court, arts. 26, 87, 90, 92(4).

¹⁴² Rules of Procedure of the Court of Justice, art. 82. At the General Court there are no Advocates General, but judges “may be called upon to perform the task of an Advocate General”.

¹⁴³ This article does not discuss custom identification by international criminal tribunals. See Arajärvi, N., The Changing Nature of Customary International Law: Methods of Interpreting the Concept of Custom in International Criminal Tribunals (Abingdon 2014)CrossRefGoogle Scholar.

¹⁴⁴ M/V “Saiga” (No. 2) (Saint Vincent and the Grenadines v Guinea) (Judgment) [1999] ITLOS Rep. 10, at [63] (UNCLOS, art. 91); M/V “Virginia G” (Panama v Guinea-Bissau) (Judgment) [2014] ITLOS Rep. 10, at [342]–[343] (UNCLOS, art. 224).

¹⁴⁵ Delimitation of the Maritime Boundary in the Bay of Bengal (Bangladesh/Myanmar) (Judgment) [2012] ITLOS Rep. 4, at [372]; M/V “Virginia G”, at [109], [430]; M/V “Norstar” (Panama v Italy) (Preliminary Objections) [2016] ITLOS Rep. 44, at [266]; Delimitation of the Maritime Boundary between Ghana and Côte d'Ivoire in the Atlantic Ocean (Ghana/Côte d'Ivoire) (Judgment) [2017] ITLOS Rep. 4, at [558]; M/V “Norstar” (Panama v Italy) (Merits) [2018-2019] ITLOS Rep. 10, at [317]–[318]; Request for an Advisory Opinion submitted by the Sub-regional Fisheries Commission (Advisory Opinion) [2015] ITLOS Rep. 4, at [144].

¹⁴⁶ M/V “Saiga” (No. 2), at [133]–[134]; Responsibilities and Obligations of States Sponsoring Persons and Entities with Respect to Activities in the Area (Advisory Opinion) [2011] ITLOS Rep. 10, at [57], [135], [145], [194].

¹⁴⁷ US–Gasoline, WT/DS2/AB/R (29 April 1996), 17; India–Patents (US), WT/DS50/AB/R (19 December 1997), at [55]; Argentina–Textiles and Apparel, WT/DS56/AB/R (27 March 1998), at [47]; Korea–Diary, WT/DS98/AB/R (14 December 1999), at [80]; Canada–Patent Term, WT/DS170/AB/R (18 September 2000), at [53]; EC–Asbestos, WT/DS135/AB/R (12 March 2001), at [115]; Chile–Price Band System, WT/DS207/AB/R (23 September 2002), at [213]; US–Softwood Lumber IV, WT/DS257/AB/R (19 January 2004), at [59]; US–Gambling, WT/DS285/AB/R (7 April 2005), at [159]; EC–Chicken Cuts, WT/DS269/AB/R WT/DS286/AB/R (12 September 2005), at [176], [192]; China–Publications and Audiovisual Products, WT/DS363/AB/R (21 December 2009), at [348]; US–Clove Cigarettes, WT/DS406/AB/R (4 April 2012), at [258]; EC–Bed Linen (Article 21.5–India), WT/DS141/AB/RW (8 April 2003), at [118]; US–Softwood Lumber V (Article 21.5–Canada), WT/DS264/AB/RW (15 August 2006), footnote 207.

¹⁴⁸ US–FSC, WT/DS108/AB/R (24 February 2000), at [166]; US–Hot-Rolled Steel, WT/DS184/AB/R (24 July 2001), at [101].

¹⁴⁹ US–Cotton Yarn, WT/DS192/AB/R (8 October 2001), at [120]; US–Line Pipe, WT/DS202/AB/R (15 February 2002), at [259].

¹⁵⁰ US–Anti-Dumping and Countervailing Duties (China), WT/DS379/AB/R (11 March 2011), footnote 222.

¹⁵¹ Varnava v Turkey (Application nos 16064/90, 16065/90, 16066/90, 16068/90, 16069/90, 16070/90, 16071/90, 16072/90, 16073/90), Judgment of 10 January 2008, at [130]; Kononov v Latvia (Application no. 36376/04), Judgment of 27 July 2008, at [120]; Laska and Lika v Albania (Application nos. 12315/04, 17605/04), Judgment of 20 April 2010, at [35]; Janowiec v Russia (Application nos. 55508/07, 29520/09), Judgment of 16 April 2012, at [140]; Wallishauser v Austria (Application no. 156/04), Judgment of 17 July 2012, at [30], [66]; Bureš v Czech Republic (Application no. 37679/08), Judgment of 18 October 2012, at [54]; Oleynikov v Russia (Application no. 36703/04), Judgment of 14 March 2013, at [66]; Čikanović v Croatia (Application no. 27630/07), Judgment of 5 February 2015, at [53]; Naku v Lithuania and Sweden (Application no. 26126/07), Judgment of 8 November 2016, at [89]; Volodina v Russia (Application no. 41261/17), Judgment of 9 July 2019, at [110].

¹⁵² Naït-Liman v Switzerland (Application no. 51357/07), Judgment of 21 June 2016, at [116]–[120].

¹⁵³ Al-Adsani v United Kingdom (Application no. 35763/97), Judgment of 21 November 2001 (GC), at [59]–[60] and 63–65; Verein gegen Tierfabriken Schweiz v Switzerland (No 2) (Application no. 32772/02), Judgment of 30 June 2009 (GC), at [36]; Guiso-Gallisay v Italy (Application no. 58858/00), Judgment of 22 December 2009 (GC), at [51]; Medvedyev and Others v France (Application no. 3394/03), Judgment of 29 March 2010 (GC), at [85]; Hirsi Jamaa v Italy (Application no. 27765/09), Judgment of 23 February 2013 (GC), at [23]; Perinçek v Switzerland (Application no. 27510/08), Judgment of 15 October 2015 (GC), at [150].

¹⁵⁴ Stoll v Switzerland (Application no. 69698/01), Judgment of 10 December 2007 (GC), at [59]; Oleynikov v Russia, at [66]; Cyprus v Turkey (Application no. 25781/94), Judgment of 12 May 2014 (GC), at [24]; Marguš v Croatia (Application no. 4455/10), Judgment of 27 May 2014 (GC), at [145]; Chiragov v Armenia (Application no. 13216/05), Judgment of 16 June 2015 (GC), at [97]; Radunović v Montenegro (Application nos. 45197/13, 53000/13, 73404/13), Judgment of 25 October 2016, at [41].

¹⁵⁵ Sabeh El Leil v France (Application no. 34869/05), Judgment of 29 June 2011 (GC), at [54].

¹⁵⁶ Naït-Liman v Switzerland (Application no. 51357/07), Judgment of 15 March 2018 (GC), at [183]–[187].

¹⁵⁷ Kononov v Latvia (Application no. 36376/04), Judgment of 17 May 2010 (GC), at [207]–[213].

¹⁵⁸ 1144 UNTS 123.

¹⁵⁹ Ibsen Cárdenas and Ibsen Peña v Bolivia (Merits, Reparation and Costs), Judgment of 1 September 2010, Series C No 217, at [193]; Vélez Loor v Panama (Preliminary Objections, Merits, Reparations, and Costs), Judgment of 23 November 2010, Series C No 218, at [290]. For a case of simple assertion unsupported by previous jurisprudence, see Arellano v Chile (Preliminary Objections, Merits, Reparations and Costs), Judgment of 26 September 2006, Series C No 154, at [153].

¹⁶⁰ Olmedo Bustos v Chile (Merits, Reparations and Costs), Judgment of 5 February 2001, Series C No 73, at [87]; Acevedo Jaramillo v Peru (Preliminary Objections, Merits, Reparations and Costs), Judgment of 7 February 2006, Series C No 144, at [176]; Arellano v Chile (Preliminary Objections, Merits, Reparations and Costs), Judgment of 26 September 2006, Series C No 154, at [97]; Abrill Alosilla v Peru (Merits, Reparations and Costs), Judgment of 4 March 2011, Series C No 223, footnote 74; Santo Domingo Massacre v Colombia (Preliminary Objections, Merits and Reparations), Judgment of 30 November 2012, Series C No 259, at [212]–[213], [216]; Pacheco Tineo v Bolivia (Preliminary Objections, Merits, Reparations and Costs), Judgment of 25 November 2013, Series C No 272, at [151]; Rights and Guarantees of Children in the Context of Migration and/or in need of International Protection, Advisory Opinion OC–21/14 of 19 August 2014, Series A No 21, at [51]; Environment and Human Rights, Advisory Opinion OC–23/17 of 15 November 2017, Series A No 23, at [129], [184].

¹⁶¹ Castañeda Gutman v Mexico (Preliminary Objections, Merits, Reparations, and Costs), Judgment of 6 August 2008, Series C No 184, at [132]; Vargas Areco v Paraguay (Merits, Reparations and Costs), Judgment of 26 September 2006, Series C No 155, at [140]; Rights and Guarantees of Children, at [211].

¹⁶² Asylum, Advisory Opinion OC–25/18 of 30 May 2018, Series A No 25, at [157]–[162].

¹⁶³ Case T-19/01, Chiquita v Commission [2005] E.C.R. II-321, at [250].

¹⁶⁴ Case T-115/94, Opel Austria v Council [1997] E.C.R. II-43, at [90]; Case T-306/01, Yusuf and Al Barakaat International Foundation v Council and Commission [2005] E.C.R. II-3544, at [232], [282]; Case T-315/01, Kadi v Council and Commission [2005] E.C.R. II-3659, at [182], [231]; Case T-231/04, Greece v Commission [2007] E.C.R. II-66, at [85]; Judgment of 14 June 2012, Stichting Natuur en Milieu v Commission, T-338/08, EU:T:2012:300, at [72]; Vereniging Milieudefensie and Stichting Stop Luchtverontreiniging Utrecht v Commission, T-396/09, EU:T:2012:301, at [61]; Front Polisario v Council, T-512/12, EU:T:2015:953, at [201]–[211]; Hamas v Council, T-289/15, EU:T:2019:138, at [172]–[173].

¹⁶⁵ Case T-115/94, Opel Austria v Council [1997] E.C.R. II-43, at [78]; Tisza Erőmű v Commission, T-468/08, EU:T:2014:235, at [321]; LTTE v Council of the European Union, T-208/11 and T-508/11, EU:T:2014:885, at [69].

¹⁶⁶ Case C-162/96, Racke v Hauptzollant Mainz [1998] E.C.R. I-3688, at [59]; Case C-192/99, R. v Secretary of State for the Home Department, ex parte Kaur [2001] E.C.R. I-1252, at [20]; Case C-344/04, R. (International Air Transport Association and European Low Fares Airline Association) v Department for Transport [2006] E.C.R. I-443, at [40]; Case C-424/05 P, Commission v Hosman-Chevalier [2007] E.C.R. I-443, at [39]; Vinkov v Nachalnik Administrativno-nakazatelna deynost, C-27/11, EU:C:2012:326, at [33]; Hungary v Slovak Republic, C-364/10, EU:C:2012:630, at [46]; Sánchez v Iberia S.A., C-410/11, EU:C:2012:747, at [21]; Manzi v Capitaneria di Porto di Genova, C-537/11, EU:C:2014:19, at [48]; Council v Front Polisario, C-104/16 P, EU:C:2016:973, at [75], [94]; AEBTRI v Nachalnik na Mitnitsa Burgas, C-224/16, EU:C:2017:880, at [62].

¹⁶⁷ Case C-162/96, Racke v Hauptzollant Mainz [1998] E.C.R. I-3659, at [24]; Case C-386/08, Firma Brita GmbH v Hauptzollamt Hamburg-Hafen [2010] E.C.R. I-1319, at [40]–[44]; Raad van bestuur van de Sociale verzekeringsbank v Evans, C-179/13, EU:C:2015:12, at [36]; Europäische Schule München v Oberto and O'Leary, C-464/13 and C-465/13, EU:C:2015:163, at [37]; Inuit Tapiriit Kanatami v Commission, C-398/13 P, EU:C:2015:535, at [50]; Air Baltic Corporation AS v Lietuvos Respublikos specialiųjų tyrimų tarnyba, C-429/14, EU:C:2016:88, at [24]; Council v Front Polisario, C-104/16 P, EU:C:2016:88, at [75], [88]; Opinion 2/15 on Competence of the Union to conclude an FTA with Singapore, EU:C:2017:376, at [161]; Western Sahara Campaign UK v Commissioners for Her Majesty's Revenue and Customs and Secretary of State for Environment, Food and Rural Affairs, C-258/16, EU:C:2018:118, at [58], [63]; Finnair v Keskinäinen Vakuutusyhtiö Fennia, C-258/16, EU:C:2018:252, at [21]; Bosphorus Queen Shipping Ltd. Corp v Rajavartiolaitos, C-15/17, EU:C:2018:557, at [67]; Guaitoli v EasyJet Airline Co. Ltd., C-213/18, EU:C:2019:927, at [47]–[48]; GN v ZU, C-532/18, EU:C:2019:1127, at [31].

¹⁶⁸ Case C-216/01, Budéjovický Budvar v Rudolf Ammersin GmbH [2003] E.C.R. I-13657, at [125]; Case C-308/06, R (International Association of Independent Tanker Owners (Intertanko) and Others) v Secretary of State for Transport [2008] E.C.R. I-4100, at [51]; Case C-118/07 P, Commission v Finland [2009] E.C.R. I-10906, at [39]; Case C-63/09, Walz v Clickair S.A. [2010] E.C.R. I-4247, at [22]–[23]; Air Transport Association of America v Secretary of State for Energy and Climate Change, C-366/10, EU:C:2011:864, at [103]–[106]; Mahamdia v Algeria, C-154/11, EU:C:2012:491, at [53]–[56].

¹⁶⁹ Case C-221/89, R v Secretary of State for Transport, ex parte Factortame Ltd. [1991] E.C.R. I-3932, at [17] (A.G. Mischo); Case C-162/96, Racke v Hauptzollant Mainz [1998] E.C.R. I-3659, at [29] (A.G. Jacobs); Case C-149/96, Portugal v Council [1999] E.C.R. I-6665, at [20]–[21], [29], [46] (A.G. Saggio); Case C-203/07 P, Greece v Commission [2008] E.C.R. I-8163, at [63] (A.G. Mazák); Case C-113/07 P, SELEX Sistemi Integrati SpA v Commission and Eurocontrol [2009] E.C.R. I-2211, at [27] (A.G. Trstenjak); Case C-118/07 P, Commission v Finland [2009] E.C.R. I-10891, at [34] (A.G. Sharpston); Case C-135/08, Rottman v Freistaat Bayern [2010] E.C.R. I-1452, at [19] (A.G. Poiares Maduro); Mahamdia v Algeria, C-154/11, EU:C:2012:309, at [26] (A.G. Mengozzi); Inuit Tapiriit Kanatami v Commission, C-398/13 P, EU:C:2015:190, at [90] (A.G. Kokott); Council v Front Polisario, C-104/16 P, EU:C:2016:88, at [94] (A.G. Wathelet); Organisation juive européenne v Ministre de l’Économie et des Finances, C-363/18, EU:C:2019:494, at [78] (A.G. Hogan).

¹⁷⁰ C-366/10, Air Transport Association of America v Secretary of State for Energy and Climate Change [2011] E.C.R. I-13765, at [125], [127]–[132] (A.G. Kokott); Raad van bestuur van de Sociale verzekeringsbank v Evans, C-179/13, EU:C:2014:2015, at [33]–[38] (A.G. Wahl); Council v Front Polisario, C-104/16 P, EU:C:2016:88, at [292] (A.G. Wathelet); Wightman v Secretary of State for Exiting the European Union, C-621/18, EU:C:2018:978, at [74] (A.G. Sánchez-Bordona).

¹⁷¹ Advocates General have examined only one element of custom (Case C-216/01, Budéjovický Budvar v Rudolf Ammersin GmbH [2003] E.C.R. I-13620, at [123]–[143] (A.G. Tizzano); Case C-621/18, Wightman, at [63]–[73] (A.G. Sánchez-Bordona)) or evidence of the elements of custom only superficially (LG v Rina SpA, C-641/18, EU:C:2020:3, at [107]–[129] (A.G. Szpunar)).

¹⁷² On transparency and legitimacy, see Grossman, N., “Legitimacy and International Adjudicative Bodies” (2009) 41 Geo. Wash. Intl. L. Rev. 107, 142–43, 152–59Google Scholar. On legitimacy in general, see Tasioulas, J., “The Legitimacy of International Law” in Besson, S. and Tasioulas, J. (eds.), The Philosophy of International Law (Oxford 2010), 97Google Scholar.

¹⁷³ A. Marmor, “Authority of International Courts: Scope, Power, and Legitimacy” in K.J. Alter, L.R. Helfer and M.R. Madsen (eds.), International Court Authority (Oxford 2018), 374, 378.

¹⁷⁴ Grossman, “Legitimacy”, 156.

¹⁷⁵ A. Buchanan, “The Legitimacy of International Law” in Besson and Tasioulas (eds.), The Philosophy of International Law, 79, 93–94.

¹⁷⁶ Thomas, C.A., “The Uses and Abuses of Legitimacy in International Law” (2014) 34 O.J.L.S. 729, 751Google Scholar.

¹⁷⁷ UN Doc A/CN.4/SR.3548 (22 July 2021), 6–7.

¹⁷⁸ Ibid.

¹⁷⁹ A, B and C v Ireland (Application no. 25579/05, Judgment of 16 December 2010 (GC), at [229]–[237]. See I. Ziemele, “Customary International Law in the Case Law of the European Court of Human Rights: The Method” (2013) 12 L.P.I.C.T. 243, 248–51.

¹⁸⁰ D. Peat, “The Tyranny of Choice and the Interpretation of Standards: Why the European Court of Human Rights uses Consensus” (2021) 53 N.Y.U.J.I.L.P. 381, 407–13.

¹⁸¹ Section IV(C)(2) above.

¹⁸² Judge Schwebel's speech to the General Assembly (26 October 1999), ICJ Yearbook (1999–2000), 282–88; Judge Guillaume's speech to the Sixth Committee of the General Assembly (27 October 2000), ICJ Yearbook (2000–2001), 326–35.

¹⁸³ Treves, T. and Hinrichs, X., “The International Tribunal for the Law of the Sea and Customary International Law” in Lijnzaad, L. (ed.), The Judge and International Custom (Leiden 2016), 25, 45Google Scholar.

¹⁸⁴ A. Seibert-Fohr, “International Judicial Ethics” in Romano, Alter and Shany (eds.), The Oxford Handbook of International Adjudication, 757, 773.