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ClientEarth Communications

15th March 2024

Protected Areas
Sustainable Seafood
Fisheries Enforcement
Fisheries Policy
Environmental justice
Climate accountability
Defending habitats
Fisheries & Seafood
Asia & the Pacific

What is the International Tribunal for the Law of the Sea (ITLOS) COSIS initiative?

In December 2022, a commission of small island states (COSIS) lodged a legal request to a tribunal in Hamburg, Germany, for an advisory opinion seeking to define the international legal obligations that States have to protect the marine environment from climate harms.

And in May 2024, the tribunal gave its advisory opinion, stating that countries have a legal obligation to reduce their greenhouse gas emissions in order to protect the ocean. 

What is an advisory opinion?

An advisory opinion is a legal clarification provided on points and questions of law. Under the UN Convention on the Law of the Sea, requests for advisory opinions can come from the International Seabed Authority or where an international agreement provides that requests can be submitted to the International Tribunal for the Law of the Sea.

What is the ITLOS advisory opinion and what did it say?

The Commission of Small Island States on Climate Change and International Law asked the International Tribunal for the Law of the Sea (ITLOS) for an advisory opinion on the scope of State obligations to protect and preserve the marine environment. Specifically, they sought to ascertain whether countries have the  obligation to reduce their greenhouse gas emissions in order to protect the ocean.

The first step was the submission of written statements by State parties and invited intergovernmental organisations (i.e. African Union, European Union, IUCN). The deadline for this was 16 June 2023. 32 States, the European Union and nine intergovernmental organisations – including COSIS, the African Union and the International Union for the Conservation of Nature – filed submissions on the content of State obligations under UNCLOS (United Nations Convention on the Law of the Sea) in light of the climate crisis.

In May 2024, the tribunal gave its advisory opinion. It said the following:

This outcome can be instrumental to push countries most responsible for the climate crisis to ramp up their ambition. Companies and financial institutions are going to feel a knock-on effect from this development too.

Lea Main-Klingst, ClientEarth lawyer

Seat of the International Tribunal for the Law of the Sea in Hamburg, Germany
What does this advisory opinion from ITLOS mean for climate law?

ITLOS' advisory opinion could be essential to the global fight against climate change. The opinion from the Tribunal that the Law of the Sea requires States all over the world to reduce their greenhouse gas emissions to prevent harm to the marine environment opens up the possibility that climate commitments - such as those made under the Paris Agreement - may need to be enforced to protect the world’s oceans. It also reinforces the idea that countries more historically responsible for climate change should step up and do more to reduce their emissions to protect the ocean than countries with smaller carbon emissions.

Next year (2025), States must improve the climate plans they submit to the United Nations - known as their Nationally Determined Contributions - and this outcome can help to push the countries most responsible for the climate crisis to ramp up their ambition. And because business must follow where governments lead, companies and financial institutions are going to feel a knock-on effect from this development, too – no matter where they operate. 

Lea Main-Klingst, ClientEarth lawyer

Domestic and international courts are increasingly being asked to define the exact nature of State obligations to curb climate change. And as the impacts become clearer and come to bear more heavily on the most vulnerable, we are likely to see courts increasingly taking the outcomes of advisory opinions into account.

What is COSIS?

The Commission of Small Island States on Climate Change and International Law (COSIS) is a collective of countries that are low-emitting, but highly vulnerable to the impacts of climate change, including rising sea levels.

COSIS was formed in 2021 at the international climate talks in Glasgow by Antigua & Barbuda and Tuvalu and is taking action to define State obligations under international law to protect the marine environment. Its members include Antigua and Barbuda, Tuvalu, Palau, Niue, Vanuatu, Saint Lucia, Saint Vincent and the Grenadines, Saint Kitts and Nevis and the Bahamas. This commission was formed after small island States became frustrated with the lack of progress made during COPs.

What does the Law of the Sea have to do with climate change?

Global warming is having significant negative impacts on the world’s seas – from ocean acidification to heating and sea level rise. Our ocean acts as the largest sink for carbon dioxide emitted from land-based sources, including industry and transportation. This excess CO2 raises the ocean’s temperatures, which has negative effects on marine life and ecosystems.

This is why COSIS sought answers on the obligations of countries under the Law of the Sea. Their question was whether State parties’ failure to limit greenhouse gas emissions, and the resulting negative effects on the marine environment, could be seen as a contravention of the Law of the Sea, and whether nations must take steps to reduce that harm.

The finding on this question opens up an essential area of law directly relevant to the climate crisis, but where obligations are still unclear – astonishing given that the ocean covers over 70% of the Earth’s surface.

“States shall take, individually or jointly as appropriate, all measures consistent with this Convention that are necessary to prevent, reduce and control pollution of the marine environment from any source, using for this purpose the best practicable means at their disposal and in accordance with their capabilities, and they shall endeavour to harmonize their policies in this connection.” - Article 194(1), Law of the Sea Convention.

How is ClientEarth involved?

ClientEarth, as well as eight other civil society organisations and the UN Special Rapporteurs on Human Rights and Climate Change, Toxics and Human Rights and Human Rights and the Environment, filed a submission to ITLOS. It does not form part of the official case file but can be accessed on the Tribunal’s website (this is an updated version of our previously published legal briefing).

In July 2024, ClientEarth, CIEL, Pacific Islands Students Fighting Climate Change and World’s Youth for Climate Justice published a joint legal memorandum on the relevance of the ITLOS advisory opinion for the advisory opinion proceedings before the International Court of Justice. The full memo can be found here.

What international climate action has already been taken?

Climate impacts such as ocean warming, acidification and rising sea levels are already disastrous for small island nations. In early March 2023, Vanuatu faced two category four cyclones within 72 hours – unprecedented in history. Island inhabitants are bringing these impacts to the world’s attention: few can forget Tuvalu’s climate minister giving a pre-COP27 address knee-deep in the ocean.

Small island States and communities are taking these concerns to the world’s highest courts and tribunals. In September 2022, Torres Strait Islanders won historic legal action against Australia, for climate-induced damages to their ancestral lands.

For decades, small island States have championed international, co-operative efforts under the existing international treaty governing climate change and greenhouse gas reductions: the United Nations Framework Convention on Climate Change, and the Paris Agreement made under it.

Now, they are also assuming leading roles in clarifying international legal obligations to push along the global efforts to mitigate and adapt to climate change.

On 29 March 2023, the United Nations General Assembly passed a resolution requesting an advisory opinion on climate change and human rights from the world’s highest court, the International Court of Justice (ICJ).

The initiative was kicked off by the Pacific Island Students Fighting Climate Change, championed by Vanuatu, and supported by World’s Youth for Climate Justice. This means the ICJ has now been asked to clarify States’ obligations to limit climate harm to the human rights of present and future generations and the environment, and the consequences under international law if they fail to do so.

Meanwhile, in January 2023, Colombia and Chile submitted a request for an advisory opinion to the Inter-American Court of Human Rights to clarify what obligations States have when it comes to climate change under the human rights treaty signed by countries throughout the Americas. It's expected that this advisory opinion will attract wider-ranging interest from States and non-governmental organisations, who also have the ability to file submissions. The deadline for written submissions on the questions before the court was 18 December 2023 and ClientEarth filed an amicus brief with the court, and appeared in the hearings in April 2024.

And just as the Vanuatu resolution passed, the highest European human rights body, the European Court of Human Rights, started for the first time to examine similar questions brought by a group of Swiss senior women and a French citizen. It handed down its decisions in April 2024.

ClientEarth filed a supportive intervention in the Swiss case (amicus), which raises novel and important questions of the interpretation of the legal duties of Switzerland to reduce its emissions to prevent harm to the elderly.

More on international court actions