Small island states advancing climate action through international law
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About COSIS
Organization of small island states united to protect the climate system
Small Island states are least responsible for climate change and bear the brunt of its effect in the short and long-term. Over the coming decades, SIDS will encounter "rising sea levels, extreme weather events, coral bleaching, loss of fisheries and marine biodiversity", as well as the risk of total submersion.
Our mission
To take collective action to protect and preserve the climate system, including the marine environment, through the promotion, progressive development, and implementation of rules and principles of international law concerning climate change.
Facing this existential threat, as well as inaction on the international stage, the Prime Ministers of Antigua and Barbuda and Tuvalu signed the Agreement for the Establishment of the Commission of Small Island States on Climate Change and International Law (COSIS) on the eve of COP26. The Agreement was registered with the United Nations in accordance with Article 102 of the Charter of the United Nations.
The organization counts nine members, in order of accession: Antigua and Barbuda, Tuvalu, Palau, Niue, Vanuatu, Saint Lucia, Saint Vincent and the Grenadines, Saint Kitts and Nevis, the Bahamas.
Membership is open to any member of the Alliance of Small Island States (AOSIS).
COSIS Treaty"The mandate of the Commission shall be to promote and contribute to the definition, implementation, and progressive development of rules and principles of international law concerning climate change, including, but not limited to, the obligations of States relating to the protection and preservation of the marine environment and their responsibility for injuries arising from internationally wrongful acts in respect of the breach of such obligations." Article 1(3) of the Agreement establishing COSIS
Activities
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Latest news
Stay informed with the latest developments in our mission to address environmental change through international law.
ICJ AO
23 July 2025
The International Court of Justice Has Released Its Advisory Opinion on the Obligations of States in Respect of Climate Change
On July 23, 2025, the International Court of Justice publicly delivered its landmark advisory opinion on the Obligations of States in Respect of Climate Change.
PRESS RELEASE IACtHR
July 3, 2025
The Inter American Court of Human Rights Has Released Its Advisory Opinion On The Climate Emergency And Human Rights
On July 3, 2025, the Inter-American Court of Human Rights publicly delivered its landmark advisory opinion OC-32/25 on the Climate Emergency and Human Rights.
Member states
United in purpose, diverse in heritage. COSIS Members are small island states representing the voices of the most vulnerable Determined to lead the fight against climate change through international law.
Antigua and Barbuda
Tuvalu
Palau
Niue
Vanuatu
Saint Lucia
St. Vincent and the Grenadines
St. Kitts and Nevis
Bahamas
Hover over a member state to learn more
Discover the unique stories and challenges of each member state in their fight against climate change.
Our work
Explore our cases, events, resources and press coverage.
ICJ
Request for an advisory opinion from the International Court of Justice (ICJ)
Resources:
- Resolution of the United Nations General Assembly adopting a resolution to request an AO on the questions included in the resolution, on March 29, 2023
- Page of the case
- Oral submissions
- Press release
- COSIS written statement
- Written reply of COSIS to the questions posed at the end of the hearing
- ICJ advisory opinion summary
ITLOS
Request for an Advisory Opinion from the International Tribunal for the Law of the Sea (ITLOS)
IACTHR
Request for an Advisory Opinion from the Inter American Court of Human Rights
From high-level event on sea-level rise at the UN headquarters, to lectures on the ITLOS advisory opinion, you will find past events on the @cosis_ccil X account.
The articles presented here offer a snapshot of global media attention on COSIS' historic case before the International Tribunal for the Law of the Sea (ITLOS) and the landmark contribution COSIS has made in the field of international law in relation to climate change.
Washington Post
Climate Tribunal Ruling Marks Victory for Small Islands
Caribbean News Global
From COP to Courtroom: ITLOS Sets New Precedents for Climate Accountability
Foreign Affairs
The International Order Isn’t Ready for the Climate Crisis
Le courrier du Vietnam
À mi-parcours, la COP26 partagée entre louanges et désillusions
Commonwealth Foundation
Climate justice: small island states push back
Caribbean News Global
Leaders of smaller islands stand up amid climate destruction and unkept promises
Jamaica Gleaner
