PIL Discussion Group: The development of International Law by the ILC and the ICJ - The case of Sea-Level Rise

Sea-level rise poses profound challenges to the foundations of international law, calling into question existing rules on maritime zones, statehood, and the protection of affected populations. This lecture will examine the respective roles of the International Law Commission (ILC) and the International Court of Justice (ICJ) in the development of international law in response to this emerging threat. Focusing on the ILC’s work on sea-level rise in relation to international law and the ICJ’s evolving jurisprudence, namely the recent advisory opinion on climate change, the lecture will discuss how these institutions contribute in complementary ways. The ILC operates as a forum for progressive development, identifying legal gaps and proposing normative responses to unprecedented factual circumstances. The ICJ, by contrast, develops the law through judicial interpretation, lending authority and stability to emerging norms. Using sea-level rise as a case study, the presentation will explore the dynamic interaction between codification, progressive development, and judicial practice, and assess the extent to which international law can adapt to climate change induced sea-level rise while maintaining legal certainty and equity for the most vulnerable States.

Patrícia Galvão Teles is a member of the United Nations International Law Commission, where she Co-Chaired the Study Group on Sea-Level Rise in relation to International Law. She is also Director-General for European and International Law at the Portuguese Ministry of Foreign Affairs, having represented Portugal in the advisory proceedings before the International Court of Justice on the Obligations of States in respect of Climate Change. She is Associate Professor at the Autonomous University of Lisbon and a member of the Permanent Court of Arbitration. She is also a member of the Institut de Droit International and of the Curatorium of the Hague Academy of International Law.