Transformation in the Approach of the International Court of Justice from Legality to Legitimacy in the Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons

Abstract

The advisory opinion of the International Court of Justice (ICJ) regarding the legitimacy of nuclear weapons created a fundamental shift in international legal reasoning, moving from a formalistic emphasis on legality to an essentialist focus on legitimacy. This article examines how the ICJ integrates broader humanitarian and environmental considerations into its interpretation of international law, particularly through the right to life, the prohibition of indiscriminate attacks, and the preservation of the environment. This shift reflects an emerging trend in the philosophy of international law that prioritizes collective human and environmental welfare over rigid state sovereignty. Key findings highlight the ICJ’s acknowledgment of the catastrophic consequences of nuclear weapons for both humanity and the environment. While the Court refrained from explicitly declaring nuclear weapons illegal, it established fundamental principles underscoring their incompatibility with humanitarian law and environmental protection. This transformation represents a broader movement in international law toward incorporating human rights and sustainability into the framework of state conduct. The study concludes by considering the implications of the ICJ’s approach for contemporary issues such as disarmament, environmental treaties, and the evolving concept of state responsibility in a globalized legal order.