By Harro van Asselt, Hatton Professor of Climate Law, Department of Land Economy and Hughes Hall, University of Cambridge; and Tejas Rao, PhD Researcher, Department of Land Economy, University of Cambridge
The Advisory Opinion on Obligations of States in Respect of Climate Change by the International Court of Justice (ICJ) is a landmark in many respects. One reason for its significance concerns its implications for one of the primary economic activities driving climate change: fossil fuel production.
Notwithstanding the obvious relevance of fossil fuel development in exacerbating the climate crisis, the topic has received little attention in the context of the international climate regime. In recent years, this has begun to change with parties to the UNFCCC and its Paris Agreement adopting several decisions that have addressed fossil fuels. However, neither the climate treaties nor these decisions spell out obligations for fossil fuel-producing States.
Fossil fuels in the ICJ proceedings
The issue of fossil fuel production, and its relevance to the Advisory Opinion, was brought up in the written proceedings by various States and organizations participating in the process. Indeed, it was deemed a matter sufficiently salient for the Court to address in a question at the closing of the oral proceedings in December 2024. At this point, Judge Cleveland asked: “During these proceedings, a number of Participants have referred to the production of fossil fuels in the context of climate change, including with respect to subsidies. In your view, what are the specific obligations under international law of States within whose jurisdiction fossil fuels are produced to ensure protection of the climate system and other parts of the environment from anthropogenic emissions of greenhouse gases, if any?”
The positions of States in response to this question can be roughly divided into three camps. The first camp, which includes several major fossil fuel-producing countries, suggest that there are no specific obligations whatsoever. The second camp, including various small island States and climate-vulnerable countries, suggest that not only can such obligations be identified, but they have already been breached by some States. A third camp, including several European and Latin American countries, occupies the middle ground, acknowledging the need to transition away from fossil fuels while emphasizing national discretion over pathways and timelines.
So how did the Court navigate these diverging positions?
Fossil fuels in the ICJ Advisory Opinion
The ICJ’s findings on the scope of the questions posed to the Court, States’ obligations, and the legal consequences arising from any breach of those obligations are all of relevance for fossil fuels.
With regard to the material scope of the questions, the Court rejected the argument put forward by some States that only activities directly generating greenhouse gas (GHG) emissions would be covered. Instead, it considered “that the material scope of its inquiry encompasses the full range of human activities that contribute to climate change as a result of the emission of GHGs, including both consumption and production activities.” In doing so, it referred specifically to the responses to Judge Cleveland’s question.
On State obligations, the Court’s finding that 1.5°C is the parties’ agreed primary temperature goal under the Paris Agreement has reverberations for phasing out fossil fuels, particularly given that several studies suggest that keeping below 1.5°C means that there is no more space for new fossil fuel development and requires a drastic phasing down of fossil fuel production.
Moreover, the Court emphasized that States do not have “unfettered discretion” in developing their nationally determined contributions (NDCs) and associated domestic measures, and that NDCs should, in aggregate, contribute to achieving the 1.5°C goal. According to the Separate Opinion by Judges Bhandari and Cleveland, this means that States’ NDCs are required to “address all fossil fuel production, licensing and subsidy activities in a manner consistent with achieving the 1.5°C temperature goal.”
The Court’s findings on customary international legal obligations are also relevant. In particular, the Court held that States must conduct environmental impact assessments (EIAs) that account for possible downstream effects, which would include integrating the end-use (Scope 3) emissions from fossil fuel burning in the EIA of a fossil fuel project, as, for example, the UK Supreme Court called for in its Finch ruling.
Lastly, the Court put fossil fuel producers and subsidizers on notice by suggesting that the “[f]ailure of a State to take appropriate action to protect the climate system from GHG emissions – including through fossil fuel production, fossil fuel consumption, the granting of fossil fuel exploration licences or the provision of fossil fuel subsidies – may constitute an internationally wrongful act.” Although the Court does not declare all fossil fuel activities illegal per se, it has shifted the burden to fossil fuel-producing States to demonstrate their activities comply with international law. In this regard, the Court’s language is unequivocal: States cannot claim ignorance about the climate impacts of resources they deliberately extract for combustion, particularly given what the Court characterizes due diligence obligations as “stringent.”
These findings directly support the implementation of SDG target 13.2 on integrating climate measures into national policies, as well as target SDG 12.c on rationalizing inefficient fossil fuel subsidies.
What’s next?
The Advisory Opinion has major implications for fossil fuel production. The very fact that the Court thought it fitting to single out the economic activities of fossil fuel production, licensing, and subsidization is telling. However, the broader effects of the Advisory Opinion will depend on how it is used, including in litigation and in international policy processes.
Within weeks of the Opinion, environmental groups in South Africa cited the Court’s EIA findings in challenging offshore drilling permits. The new Milieudefensie case against Shell is also likely to leverage the Court’s reasoning on downstream emissions. Although the emergence of contentious litigation at the international level is an open political question, the Advisory Opinion could be read to suggest that developed countries that are also major fossil fuel producers are at greater risk of being challenged.
As regards international policy processes, the issue of fossil fuels will likely come up at the UN Climate Change Conference in Belém (UNFCCC COP 30) in November. However, some parties already resist the inclusion of fossil fuel transition language in COP decisions. This resistance is likely to intensify given the ICJ’s findings. Parties opposing stronger fossil fuel language may now fear that any COP decision could potentially be used in the interpretation of the climate treaties.
For States preparing for COP 30, three actions become critical:
- Incorporate measures addressing fossil fuel production and subsidies into updated NDCs, as the Court’s findings suggest these activities should be covered.
- Reform EIA procedures to assess Scope 3 emissions, aligning domestic law with the Court’s interpretation.
- Phase out public financial support for fossil fuels with clear timelines, recognizing the Court’s characterization of such support as potentially wrongful.
Feuds over fossil fuels will proceed both in courtrooms and in conference halls. However, through its Advisory Opinion, the ICJ has handed advocates for a fossil fuel phase-out important tools to strengthen their legal case. While the Court stopped short of declaring a legal obligation to phase out fossil fuels, it has fundamentally altered the legal landscape by establishing that continued fossil fuel expansion must be justified against stringent due diligence standards and the 1.5°C imperative. States continuing to license new projects or subsidize production now bear the burden of proving their actions comply with stringent climate obligations. With the Advisory Opinion, international law is at long last catching up with climate science on fossil fuels.
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This Guest Article is part of a project that seeks to raise awareness and build momentum and knowledge around the ICJ advisory opinion on obligations of States in respect of climate change and to promote a better understanding of the implications of the advisory opinion among sustainable development decision makers.