Legal Memorandum Advisory Opinion on Climate Change Delivered by the International Tribunal for the Law of the Sea: Relevance for the International Court of Justice Climate Advisory Proceedings

This legal memorandum by the Center for International Environmental Law (CIEL) analyzes the May 21, 2024, advisory opinion (AO) from the International Tribunal for the Law of the Sea (ITLOS) regarding States' obligations to protect oceans from climate change. The document details how the ITLOS AO defines anthropogenic greenhouse gas (GHG) emissions as marine pollution under the UN Convention on the Law of the Sea (UNCLOS) and discusses the implications of this ruling for ongoing climate advisory proceedings before the International Court of Justice (ICJ).

• The International Tribunal for the Law of the Sea (ITLOS) concluded that anthropogenic greenhouse gas (GHG) emissions into the atmosphere meet the three cumulative criteria of UNCLOS Article 1(1)(4) and therefore constitute "pollution of the marine environment".
• Under UNCLOS Article 192, States have a legal obligation to protect and preserve the marine environment from ocean acidification and climate change impacts, including adaptation and resilience actions. This obligation requires a "stringent" standard of due diligence because of the high risk of irreversible harm.
• UNCLOS Article 194 requires States to take all necessary measures to prevent, reduce, and control marine pollution from anthropogenic GHG emissions. The ITLOS AO specifies that compliance with the Paris Agreement alone is insufficient to meet this obligation, as the Paris Agreement is not lex specialis and does not supersede UNCLOS.
• The ITLOS AO establishes that the "best available science," specifically the works of the Intergovernmental Panel on Climate Change (IPCC), is the objective benchmark for determining the necessary measures States must take to meet their legal obligations.
• Regarding equity, the Tribunal ruled that while all States must make mitigation efforts, those with greater capabilities must do more. However, a lack of means cannot be used as an excuse to exempt a State from its obligation to take all necessary measures.
• The ITLOS AO clarifies that the obligation to conduct environmental impact assessments (EIAs) is customary international law and must include the cumulative impacts of activities, as well as potential socio-economic impacts. This implies that downstream (scope 3) emissions from projects, such as fossil fuel projects, must be analyzed.
• The Tribunal reaffirmed the duty to prevent transboundary harm, stating that UNCLOS imposes a more stringent obligation to prevent the "spread" of pollution than the principles found in the Rio or Stockholm Declarations.
• The ITLOS AO warns that marine geoengineering could violate UNCLOS Article 195 if it transforms one type of pollution into another, and may be subject to Article 196 regarding the use of technologies under a State's control.

APA

Center for International Environmental Law (2024). Legal Memorandum Advisory Opinion on Climate Change Delivered by the International Tribunal for the Law of the Sea: Relevance for the International Court of Justice Climate Advisory Proceedings. https://www.ciel.org/wp-content/uploads/2024/07/Final_-Legal-Memorandum_-Relevance-of-ITLOS-climate-AO-for-the-ICJ-AO_CIEL_July-2024.pdf

Chicago

Center for International Environmental Law. Legal Memorandum Advisory Opinion on Climate Change Delivered by the International Tribunal for the Law of the Sea: Relevance for the International Court of Justice Climate Advisory Proceedings. 2024. https://www.ciel.org/wp-content/uploads/2024/07/Final_-Legal-Memorandum_-Relevance-of-ITLOS-climate-AO-for-the-ICJ-AO_CIEL_July-2024.pdf.

Wikipedia

{{cite report |author=Center for International Environmental Law |title=Legal Memorandum Advisory Opinion on Climate Change Delivered by the International Tribunal for the Law of the Sea: Relevance for the International Court of Justice Climate Advisory Proceedings |date=July 2024 |url=https://www.ciel.org/wp-content/uploads/2024/07/Final_-Legal-Memorandum_-Relevance-of-ITLOS-climate-AO-for-the-ICJ-AO_CIEL_July-2024.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{centerforinternationalenvironmentallaw2024legal, author = {{Center for International Environmental Law}}, title = {{Legal Memorandum Advisory Opinion on Climate Change Delivered by the International Tribunal for the Law of the Sea: Relevance for the International Court of Justice Climate Advisory Proceedings}}, institution = {Center for International Environmental Law}, year = {2024}, month = jul, url = {https://www.ciel.org/wp-content/uploads/2024/07/Final_-Legal-Memorandum_-Relevance-of-ITLOS-climate-AO-for-the-ICJ-AO_CIEL_July-2024.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }