On 21 May 2024, the International Tribunal for the Law of the Sea (ITLOS) released an Advisory Opinion. This is a momentous occasion — it is the first time that an international tribunal has issued an opinion on the obligation of States to mitigate climate change.

The Opinion outlines what specific obligations there are on States which are parties to the United Nations Convention on the Law of the Sea (UNCLOS) to: prevent, reduce and control pollution of the marine environment in relation to the effects of climate change which are caused by human-induced greenhouse gas (GHG) emissions into the atmosphere; and to protect and preserve the marine environment in relation to climate change impacts.

The 21 judges of the Tribunal unanimously advised that:

  • human-induced GHG emissions constitute ‘pollution of the marine environment’;
  • States Parties have a specific obligation to take all necessary measures to prevent, reduce and control marine pollution caused by human-induced GHG emissions;
  • they also have a specific obligation to assist developing States, in particular vulnerable developing States, in their efforts to address marine pollution from human-induced GHG emissions; and
  • they have a specific obligation to take measures necessary to conserve the living marine resources threatened by climate change impacts and ocean acidification.

The result? The Opinion says States Parties must take into account the best available science and relevant international rules and standards, but what actions are necessary will vary depending on the capabilities of the State. The obligations are described as stringent ‘due diligence’ obligations, meaning States Parties must not only develop strategies to deal with marine pollution and protection of the marine environment, but monitor them to ensure they are actually effective. In other words, it shouldn’t be a box ticking exercise.

Crucially, ITLOS also decided that the above obligations cannot be met by simply complying with the States’ obligations under the Paris Agreement. It found that while the Paris Agreement complements UNCLOS in relation to the obligation to regulate marine pollution, it does not supersede it. The result is that States Parties to UNCLOS, including Australia, cannot point to their compliance with their obligations under the Paris Agreement to say that they have complied with UNCLOS.

Australia, among 168 other parties (of which the United States is not one), will need to collaboratively develop scientifically-appropriate policies and systems to prevent, reduce and control marine pollution caused by human-induced GHG emissions and to conserve living marine resources.

In 2023, Australia was the 14th highest emitter of GHG. The ITLOS Advisory Opinion shows that although climate change is a global problem, States still have individual responsibility to take systemic and effective action. Although the Opinion is not legally binding, it will pave the way for precedent-forming decisions which will bind States. Furthermore, it provides an advocacy tool for developing States to hold industrialised States to account for failing to assist them in mitigation efforts.

The International Court of Justice and the Inter-American Court of Human Rights are also due to shortly deliver opinions on climate change.