Judicial Legislation, Not Lawmaking: How the ICJ Fills Legal Gaps Without Creating New Law

Document Type : Original Article

Author

University of Technology Sydney, Australia

Abstract

The International Court of Justice (ICJ) often faces criticism for allegedly exceeding its mandate by engaging in what some perceive as lawmaking. This debate, though not new, continues to spark significant scholarly discourse and is even echoed by some of its own judges. Although the ICJ consistently denies having a lawmaking function, its practices demonstrate its role in the development of international law. This raises the question: How can the Court contribute to the development of international law, particularly in addressing gaps, if it lacks formal lawmaking capacities? Are the criticisms of the Court exceeding its mandate valid? Existing literature often conflates ‘judicial legislation’ with ‘lawmaking’, creating a bottleneck in reasoning which causing scholars to necessarily conclude that the ICJ inevitably exceeds its judiciary mandate and engages in creating new laws. However, understanding the ICJ’s role in developing international law and addressing gaps, despite its statutory limitations, requires distinguishing between ‘judicial legislation’ and ‘lawmaking’. While the latter involves creating new laws, ‘judicial legislation’ refers to a method of interpretation for adapting existing laws and establishing new legal relationships to address emerging legal requirements. This article goes further to identify which types of interpretation are most effective for such judicial legislation. By examining the approaches of the UN International Law Commission (ILC), the article highlights ‘evolutive interpretation’ as a particularly suitable method. Evolutive interpretation enables the Court to rejuvenate existing laws, clarify ambiguities, and develop legal frameworks for unregulated issues – all while staying within its adjudicative-only mandate and avoiding lawmaking.

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Iranian Journal of International and Comparative Law

Articles in Press, Accepted Manuscript
Available Online from 13 May 2025

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