DLA Piper advises four developing nations in groundbreaking ICJ Advisory Opinion on climate change responsibility

Global law firm DLA Piper has advised the Governments of the Democratic Republic of Timor-Leste, the Kingdom of Tonga, Solomon Islands, and the Republic of Zambia pro bono in the hearings in the advisory opinion on the Obligations of States in respect of Climate Change before the International Court of Justice (ICJ).

The ICJ released its first advisory opinion on climate change on 23 July 2025. Its unanimous opinion clarified that states have legally binding obligations under international law to protect the climate system from greenhouse gas emissions, including duties under climate treaties, other environmental treaties, the law of the sea, customary international law, and human rights law. ICJ found that states can be held responsible for internationally wrongful acts when they fail to exercise due diligence in regulating emissions, including from private actors/corporations under their jurisdiction.

When states breach these obligations, they must cease the wrongful conduct and provide full reparation through restitution, compensation, or satisfaction to injured states that can demonstrate a sufficiently direct causal link to the harm suffered. The ICJ observed that temporal scope, causation and related issues of responsibility would need to be assessed on the facts of a specific case (ie in concreto) for the determination of State responsibility, which was beyond the scope of the present Opinion, but not impossible in the climate change context.

Partner Stephen Webb said: “The advisory opinion provides much needed clarity on the responsibilities of states to not only take action on climate change, but also to support Small Island Developing States to respond to the impacts of climate change. This proceeding was truly Pacific-led, and we acknowledge the incredible efforts of the Pacific Islands Students Fighting Climate Change and the Vanuatu Government for spearheading this initiative.”

While appearing as Agent for Tonga, Partner, Gitanjali Bajaj stated that there is a “need for individual and collective transformative action to combat the climate crisis and change the course in which humanity is heading.”

International Head of Pro Bono Claire Donse added: “By taking these cases on a pro-bono basis, we help give those states most vulnerable to climate risk an opportunity to share their perspectives from the frontlines of climate change and shape the development of international environmental law for the benefit of like-minded states.”

The United Nations General Assembly, by consensus, requested the ICJ provide an advisory opinion on the obligations of states under international law to protect the climate system from the adverse effects of anthropogenic greenhouse gas emissions for states, and for present and future generations. The ICJ was asked to consider the legal consequences for states that have caused significant harm to the climate. You can read more about the significance of the proceedings here. The international participation in this proceeding was unprecedented, with 98 states and 12 international organisations making submissions over a two-week hearing from 2 to 13 December 2024, demonstrating the importance

The ICJ proceedings follow the climate change advisory opinion before the International Tribunal for the Law of the Sea (ITLOS) on states’ obligations to protect the marine environment from the impacts of climate changes. DLA Piper also supported Timor-Leste in those proceedings.

The international cross-practice DLA Piper team comprised partners Stephen Webb, Gitanjali Bajaj, Claire Donse, Catriona Martin and senior associates Claire Robertson, Milly Thomas, solicitors Riley Arthur, Saoirse O'Dea, Benjamin Crowley, Paivi Adeniyi, and Eran Sthoeger Esq. as Counsel for Timor-Leste, Harj Narulla as Counsel for Solomon Islands, and Professor Christian Tams and Olivia Flasch as Counsel for Zambia. The DLA Piper team was also supported by John Ridgway, Dirk Heinz, Damian Kelly, and other members of Pacific Legal Network in relation to Solomon Islands.