A critical Analysis of the ICJ’s Identification of Customary International Law in the 2023 Judgment of <i>Nicaragua v. Colombia</i>

Abstract In the 2023 judgment of Nicaragua v. Colombia , the International Court of Justice ruled that, under customary international law, a State’s entitlement to a continental shelf beyond 200 nautical miles from its baselines is not permitted to extend within 200 nautical miles from the baselines of another State. In identifying this customary rule, the Court did not apply the two-element approach. The state practice relied upon by the Court to identify the general practice is not sufficiently widespread, representative, or consistent. The opinio juris is inferred from such state practice, which is not necessarily driven by a sense of legal obligation. The Court’s assertion of the customary rule constitutes, in effect, a rewriting of the relevant provisions of the United Nations Convention on the Law of the Sea, amounting to a legislative exercise.