1 The Conclusions’ text is also appended to the authors’ manuscript, in the form of Annex 1 (pp. 302–05, attaching the Conclusions) and Annex 2 (pp. 307–44, attaching the Conclusions “with commentaries”).

2 ILA (Study Group on) Principles on the Engagement of Domestic Courts with International Law, Final Report: Mapping the Engagement of Domestic Courts with International Law, 5, paras. 11–12 (2016), at https://www.ila-hq.org/en_GB/documents/conference-study-group-report-johannesburg-2016 (original emphasis omitted).

3 Noting Wood’s agreement, as ILC rapporteur, with other ILC members, that “the word ‘rules’ should be avoided in the conclusion dealing with the scope of the topic, so as not to ‘take the risk of reopening the debate on the nature of those rules’” (p. 51).

4 Diego Mejía-Lemos, On Self-Reflectivity, Performativity, and Conditions for Existence of Sources of Law in International Law, 57 Ger. Y.B. Int’l L. 289, 294, 317 (2014).

5 Diego Mejía-Lemos, Custom and the Regulation of “the Sources of International Law,” in The Theory, Practice, and Interpretation of Customary International Law (Panos Merkouris, Jörg Kammerhofer & Noora Arajärvi eds., 2022).

6 Prosecutor v. Vlastimir Đorđević, Case IT-05–87/1-A, Appeals Judgment, para. 33, n. 117 (Jan. 27, 2014) (stating that “Article 38(1) of the Statute of the International Court of Justice … is regarded as customary international law.”), discussed in Mejía-Lemos, supra note 5, at 137–38.

7 Mejía-Lemos, supra note 5, at 137–38.

8 The research project “The Rules of Interpretation of Customary International Law” received funding of €1,480,708.00 by the European Research Council, at https://cordis.europa.eu/project/id/759728/results.

9 Military and Paramilitary Activities in and Against Nicaragua (Nicar. v. U.S.), Judgment, 1986 ICJ Rep. 14, para. 178 (June 27).

10 Of course, “the generation of customary law cannot be mathematically … decided” (p. 160). On a related note, although the impact of technology on “[a]ccess to evidence” of CIL is considered, no reference is made to “artificial intelligence” among those forms of “information technology of the digital era” (p. 27), which, alongside “text-as-data tools, may contribute to accessing and assessing practice” (p. 27 n. 110).

11 Certain German Interests in Polish Upper Silesia (Ger. v. Pol.), 1926 PCIJ (Ser. A) No. 7, at 19 (May 25).

12 North Sea Continental Shelf (Ger. v. Den.; Ger. v. Neth.), Judgment, 1969 ICJ Rep. 3, para. 74 (Feb. 20).

13 Nicar. v. U.S., supra note 9, para. 207 (requiring “evidence of a belief” to that effect.)

14 Right of Passage Over Indian Territory (Port. v. India), Judgment, 1960 ICJ Rep. 6, 40 (Apr. 12).