From Ascertainment to Anticipation The International Court of Justice's Rules-based and Relational Governance in Identifying Customary International Law

Abstract

The International Court of Justice's strategies for identifying customary international law in both its contentious and advisory proceedings are often viewed as expressions of judicial impartiality. Its reliance on treaties codifying customary norms as well as on functional or equitable reasoning reflects the institutional constraints of its mandate. However, these constraints are not the sole drivers of its approach. The relational nature of international law-particularly the conditions under which norms gain binding force-also shapes the Court's identification strategies. The relational normativity of customary international law highlights the inescapable role of politics in the Court's work as it navigates questions of trust, legitimacy and compliance. In this light, the Court functions not only as a judicial body but also as a political actor whose legitimacy depends on balancing rules-based and relational governance before the bench and outside the courtroom.