The ICJ’s application of the law of the sea in its climate change advisory opinion: a critical assessment

Abstract

The convergence of the climate and ocean agendas has become a defining feature of contemporary global governance. In its advisory opinion on climate change, the International Court of Justice (ICJ) advanced this convergence by endorsing the advisory opinion delivered by the International Tribunal for the Law of the Sea (ITLOS) and treating the law of the sea as part of the most directly relevant applicable law. However, the ICJ’s approach to interpreting and applying the law of the sea reveals insufficient justification for selecting the United Nations Convention on the Law of the Sea (UNCLOS) as the applicable law, a contested application of the principle of systemic integration, and an evolutionary interpretive approach with a tendency toward judicial law-making. Objectively assessed, the ICJ’s advisory opinion on climate change strengthens the coherence of international climate law and may encourage substantive climate action but also creates challenges for climate governance under UNCLOS. The expansion of climate obligations through treaty interpretation may further discourage States from assuming responsibility where the boundaries of such responsibility are increasingly blurred. In the long term, international judicial bodies, represented by the ICJ, and Small Island Developing States (SIDS) should reflect on the potential and limitations of advisory opinions and reconsider the future integration of climate and ocean law regimes.