The Relevance of the ICJ and ITLOS Advisory Opinions for the Climate Regulation of Maritime Transport: A Reappraisal of MARPOL

Resumen

Maritime transport is essential to global trade but remains a significant source of greenhouse gas (GHG) emissions. This paper aims to assess the relevance of the advisory opinions issued by the International Tribunal for the Law of the Sea (ITLOS) in 2024 and the International Court of Justice (ICJ) in 2025 for the climate regulation of maritime transport, with particular attention to MARPOL Annex VI and the No More Favourable Treatment (NMFT) principle. Methodologically, it adopts a doctrinal legal approach, combined with systemic analysis and informed by the technical and institutional context of maritime decarbonization, through the review of primary sources and specialized scholarship. The analysis finds that the ICJ Advisory Opinion clarifies the scope and standard of States’ climate-related due diligence obligations, while the ITLOS Advisory Opinion confirms that anthropogenic GHG emissions may fall within the definition of marine pollution under UNCLOS. The paper concludes that, read together, these opinions support a systemic reappraisal of MARPOL Annex VI and reinforce the rationale of NMFT as a mechanism for the practical universalization of maritime climate-related standards, particularly as the IMO Net-Zero Framework moves towards more demanding fuel-intensity and economic measures.