The independent judicial body ITLOS on Tuesday has confirmed that human-caused greenhouse gas emissions constitute ‘pollution of the marine environment’ and that States therefore must comply with a wide-ranging set of obligations under the United Nations Convention on the Law of the Sea (UNCLOS).

In its ruling – an “advisory opinion”- the International Tribunal for the Law of the Sea (ITLOS) clarifies States’ obligations under UNCLOS with respect to impacts from anthropogenic climate change on the marine environment.

The judicial body has handed down an advisory opinion which is a response to a request by a collective of small island states called the Commission of Small Island States on Climate Change and International Law (COSIS), which was issued in December 2022.

The international court said states have a legal obligation to prevent, monitor and reduce the emissions that contribute to climate change and laid out specific requirements under the law of the sea to protect the ocean from the impacts of anthropogenic climate change, including international shipping.

The Tribunal has also made clear that simply participating in global efforts is not necessarily enough to meet this standard.

The news came to light by Opportunity Green, an NGO working to unlock the opportunities from tackling climate change using law, economics, and policy.

Opportunity Green’s submission to the Tribunal outlined the fact that UNCLOS requires States to take all necessary measures to prevent, reduce and control pollution of the marine environment including GHG emissions from vessels in line with the 1.5°C temperature goal of the Paris Agreement.

As long as climate policies enacted by the IMO remain unaligned with the Paris Agreement temperature limit, States are failing to meet their obligations under UNCLOS and that can and should adopt more stringent unilateral or regional standards to meet their obligations under UNCLOS.

This advisory opinion comes at the time when States at the International Maritime Organization (IMO) this September will continue the negotiations around the ‘basket of measures’ that will support the delivery of the Revised GHG Strategy agreed last year, as Opportunity Green explains in its statement.

Last year, Opportunity Green put forward a supporting submission to ITLOS urging the Tribunal to consider international shipping emissions in its opinion.

The submission called on the Tribunal to clarify countries’ legal obligations to stop the pollution of the marine environment and protect it from climate change impacts.

David Kay, legal director of Opportunity Green, said: “This is a seminal moment for international climate change law.

“The judges were clear that given the high risks of serious and irreversible harm to the marine environment, states’ obligations to address GHG emissions need to meet a very high standard, informed by the best available science and the 1.5 degree temperature goal and timeline.

“It’s not enough to just rely on global efforts and international organisations. With sectors such as international shipping currently off course, States urgently need to put in place effective policies to meet these legal obligations.”