Climate impact litigation strengthened with ICJ opinion

Background

On 23 July 2025, the President of the International Court of Justice (ICJ) (considered the World's court) in The Hague, Netherlands, Judge Iwasawa Yuji, delivered the ICJ's advisory opinion on the obligations of States in respect of climate change.  Hailed as an "historic achievement which sets the benchmark for climate action going forward", this keenly awaited opinion was, surprisingly, derived from students in the Pacific Island State of Vanuatu seeking to fight the climate crisis.  In an attempt to force richer nations, who have contributed the most to greenhouse gas (GHG) emissions, not only to listen to the vulnerable smaller countries taking the brunt of it on the front line, but to be held accountable, they sought sponsors from other UN Member States.  The opinion was the culmination of two years' work, the ICJ having been asked in 2023, by the UN General Assembly (UNGA), two questions: 

1. As a matter of international law, what are States' obligations, "to ensure the protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases for States and for present and future generations"; and

2. Under those obligations, what are the legal consequences for States, "where they, by their acts and omissions, have caused significant harm to the climate system and other parts of the environment, with respect to:
(i) States, including, in particular, small island developing States, which due to their geographical circumstances and level of development, are injured or specially affected by or are particularly vulnerable to the adverse effects of climate change?
(ii) Peoples and individuals of the present and future generations affected by the adverse effects of climate change?”

There was record participation from States, global institutions, legal experts and civil society from around the world.  The ICJ received 91 written statements with 62 written comments on those for the ICJ to consider during the preliminary stage.  This far exceeded any former advisory proceedings in the ICJ.  During the next stage, in December 2024, when States and organisations were given the opportunity to provide additional oral testimony, 96 States and 11 international organisations took part, many for the first time.  Following conclusion of the hearings, 65 responses were provided to the judges' further questions on fossil fuel production, mitigation under the Paris agreement, entitlement to environmental health and States' liability for loss and damage.

Opinion

Whilst the ICJ did not hold individual nations accountable, it was made clear that States will be held responsible where they do not adhere to laws protecting the climate from GHG emissions, including those attributable to fossil fuels.  Breaches will be assessed on a case-by-case basis and redress, if found legally liable, could include cessation, undertaking not to repeat that behaviour and full reparation (restitution and compensation). 

Under the Paris Agreement on climate change, a threshold figure of 1.5°C was set.  The Intergovernmental Panel on Climate Change (the IPCC), the body the ICJ considers is providing the best available science on climate change, deems this an unsafe temperature warming.  Where States set their own targets (nationally determined contributions or NDCs) under the Paris Agreement, the IPCC highlights:

• States' discretion to do so is not unrestricted.

• When setting goals, targets should reflect the best possible standard matching their contribution to GHG emissions.

• Individual targets will be aggregated with other States to meet the 1.5% temperature goal of the Paris Agreement.

• States are obliged to use their best endeavours to meet their targets.

The opinion goes on to say States' obligations stretch beyond climate treaties (which it recognises the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement are the key legal instruments used to combat climate change globally).  Applicable laws with respect to States' obligations, also stems from international law (with a recognised duty to prevent significant harm to the environment and therefore an obligation to act with due diligence), other treaties (observing the United Nations Convention on the Law of the Sea, the ozone treaties, the United Nations Convention on Biological Diversity and the United Nations Convention to Combat Desertification are also directly applicable laws) and international human rights laws (safeguarding human rights which includes the right to a healthy and sustainable environment). 

Many have commented on this including UN Secretary-General, António Guterres, issued a video message, saying "This is a victory for our planet, for climate justice and for the power of young people to make a difference."  The Alliance of Small Island States, which are one of the nations on the front line of climate change, welcomed the opinion as, "a global affirmation that climate harm is not just unjust, it is unlawful".  Succinctly put by Ralph Regenvanu, the climate minister for the Pacific Island State of Vanuatu, where this all began, the opinion "goes beyond what we dared hope".

Key takeaways

• Whilst not technically legally binding, this opinion strengthens legal action against States for accountability over the climate crisis, including historic cases.We will no doubt see even more climate impact litigation (such as the Carbon Majors cases in the US courts we wrote about in our Annual Insurance Review 2024 and the long-running case of Lliuya v RWE which you can read about in our article here) and we expect cases are being prepared now with this opinion firmly in hand.

• The legal consequences can include monetary compensation.

• States cannot set their own climate targets without reference to the Paris Agreement or consideration of other States' targets.