On 23 July 2025 the International Court of Justice (ICJ) delivered its Advisory Opinion on the Obligations of States in Respect of Climate Change (the Advisory Opinion). In this blog, we draw out key themes of the Advisory Opinion which are relevant to public authorities and the private actors who they regulate and whose rights they must respect.
Key points
- The Advisory Opinion is not binding but sends a clear signal to States regarding their international law obligations concerning climate change.
- The Advisory Opinion emphasises that State responsibilities are 'stringent' and that they have substantive and procedural obligations (eg with respect to Nationally Determined Contributions (NDCs) and Environmental Impact Assessments (EIAs)) which afford them limited discretion.
- The Advisory Opinion may lead to heightened scrutiny and regulation in connection with the consumption and production of, and licences and subsidies related to, non-renewable fuels, which may have significant implications for commercial organisations.
- It is yet to be seen whether the European Court of Human Rights (ECtHR) will go further than it has done in recent cases involving climate change such as Verein KlimaSeniorinnen Schweiz and Others v. Switzerland (App. 53600/20)(the VKS Case).
Background
On 12 April 2023 the Secretary General of the United Nations issued a request for an Advisory Opinion to the ICJ, pursuant to UN General Assembly Resolution 77/276, which was the result of a campaign led by small island states including Vanuatu. The two questions for the ICJ related to: (1) the identification of the obligations of States with respect to climate change as a matter of international law; and (2) the consequences of breaching such obligations (if any). The Advisory Opinion is non-binding but, as a statement from the 'World Court' on a topic of general application, it will influence regional and domestic courts including in the United Kingdom.
Key themes and commentary
The Advisory Opinion is extremely broad in scope. We have broken down further details in our blog post here. In this blog, we focus on four key themes relevant to public law and regulation in the United Kingdom.
- Increased pressure on public authorities and corporate actors
The Advisory Opinion is the latest and the largest in scope in a series of similar advisory opinions from the International Tribunal for the Law of the Sea and the Inter-American Court of Human Rights (covered in previous blog posts here and here respectively). Viewed in this context, the fact that the 'World Court' has now delivered its much anticipated Advisory Opinion emphasising the responsibility of States for climate change is a clear signal of the increasingly urgent global need to mitigate climate change. The Advisory Opinion is clear that on the one hand, the conduct of any organ of a State is attributable to that State, and on the other hand, a State is also responsible for regulation of 'private actors' and 'planned activities'within theirjurisdiction or control. The implication may be that public authorities and the corporate actors they regulate come under increasing scrutiny, as State leaders seek to limit the liability that might be attributed to the State.
- Stringent responsibilities and limits on discretion for States
The ICJ repeatedly emphasised that obligations of States with respect to climate change are 'stringent'and, although the manner in which States may carry out some of their duties is discretionary (eg the 'duty to co-operate for the protection of the environment'), there are certain concrete obligations which afford limited discretion. These include a substantive obligation to prepare, communicate and maintain NDCs under Article 4 of the Paris Agreement and a procedural obligation to conduct EIAs pursuant to States' duty to exercise due diligence in preventing significant harm to the environment (which may be implemented through specific domestic, regional or international laws or treaties). The ICJ held that 'the discretion of parties [to the Paris Agreement] in the preparation of their NDCs is limited'and that the measures set out in an NDC must, when taken together with those of other States, be 'capable of achieving the temperature goal of limiting global warming to 1.5°C above pre-industrial levels'. As to EIAs, the ICJ held that 'specific climate-related effects must be assessed ... at the level of proposed individual activities' and made a specific reference to their 'possible downstream effects'(see our latest blog relating to the assessment of likely downstream emissions in EIAs).
- Likelihood of tighter scrutiny and regulation concerning non-renewable fuels
Since the ICJ held that the conduct of any organ of State is attributable to that State, and this includes both their acts and omissions, public authorities might be pressured to tighten scrutiny and regulation of private actors and planned activities, particularly in respect of non-renewable fuels. The ICJ gave the examples of 'fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies'as activities which may amount to the failure of a State to take appropriate action to protect the climate system from greenhouse gas emissions and may constitute an internationally wrongful act which is attributable to States.
The ICJ also confirmed that States have a 'duty of cessation' in relation to their wrongful acts, and that this duty 'may require a State to revoke all administrative, legislative and other measures that constitute an internationally wrongful act of that State'.It is not possible for a court to 'revoke' or invalidate primary legislation in the United Kingdom, but courts can invalidate administrative measures (including secondary legislation) if an aggrieved party challenges these successfully by way of judicial review. Parliament can also repeal primary legislation.
- Developments in human rights law
The ICJ found that because a healthy environment is necessary for, and inherent in, the enjoyment of other human rights explicitly enumerated in treaties, it must follow that humans have a right to a clean, healthy and sustainable environment. Although some national and regional courts and institutions had expressed this view before, the Council of Europe and ECtHR had not gone so far as to find that the explicit rights in the European Convention on Human Rights (ECHR) (which is implemented in domestic law in the United Kingdom via the Human Rights Act 1998) necessarily implied an actionable right to a healthy environment.
Rather, in the VKS Case, the ECtHR held that State parties to the ECHR had a positive obligation to mitigate climate change because climate change can interfere with an individual's quality of life, which is itself protected by Article 8 of the ECHR (as explained in further detail in our blog on the VKS Case). It remains to be seen whether the ECtHR's case law will continue to develop along the lines set out in the Advisory Opinion.
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