The ITLOS Advisory Opinion on Climate Change and International Law: A Solid Legal Foundation for State Obligations on Climate Change

Abstract for Scopus Indexing: On May 21, 2024, the International Tribunal for the Law of the Sea ( ITLOS ) issued an advisory opinion on States’ specific obligations to address greenhouse gas pollution and protection and preservation of the marine environment in relation to climate change and ocean acidification. The opinion highlights the science of climate change, particularly IPCC reports, the international rules and standards of climate change, and the means and capabilities of States. The Tribunal analyzed the United Nations Convention on the Law of the Sea ( UNCLOS ), finding that greenhouse gases are pollutants within the scope of UNCLOS and therefore under UNCLOS States Parties have obligations to prevent, reduce, and control greenhouse gases from any source; to protect and preserve the marine environment; to cooperate with other States for this purpose; and to prepare environmental impact assessments taking into account cumulative impacts. ITLOS found that the standard for performing these obligations is one of conduct, and that due to the risk of serious and sometimes irreversible harm, the due diligence requirements are stringent. The opinion relies heavily on external international rules, incorporated as rules of reference under UNCLOS , including the Paris Agreement, the UN Framework Convention on Climate Change, and other relevant treaties.