A growing number of cases worldwide are challenging State approval of new fossil fuel projects: from Ireland to Guyana, Greece to South Africa. UN Secretary General, António Guterres, describes such projects as “moral and economic madness”. But since 2021, over 2,300 new extraction projects and 119 new LNG Terminals have been approved for development worldwide. New fossil fuel projects cannot operate without State authorisation.

Courts are beginning to grapple with the legality of these approvals. In Greenpeace Nordic and Others v. Norway (People v. Arctic Oil), the European Court of Human Rights (ECtHR) found that States are required by Article 8 to assess whether approval of new petroleum projects, given their global climate impacts, is compatible with their national and international obligations. (para. 419) This requirement was subsequently enforced by a Norwegian appeals court in Greenpeace Nordic and Nature & Youth v. Energy Ministry (North Sea Fields), which overturned several oil production licences partly because such an assessment had not been conducted. (p. 27)

With the procedural obligation to assess both climate impacts and legal compatibility now clarified, future cases will test whether States can substantively justify their approval of new projects, considering the requirement to limit global warming to 1.5ºC above pre-industrial temperatures. In particular, courts will assess whether approval is compatible with States’ obligations, as articulated by the International Court of Justice (ICJ) Advisory Opinion on climate change, to prevent significant harm to the climate system; to respect, protect, and fulfil human rights; and, for Annex I countries, to conserve and enhance reservoirs of greenhouse gases.

This blog argues that, when you apply the latest science to the latest law as articulated by international, regional and national courts, States’ approval of new fossil fuel projects is fundamentally incompatible with their international law duties. It also sets out what comes next for domestic cases that seek to enforce this negative duty.

States may be liable for the harm caused by new fossil fuel projects

Until recently, fossil fuel production did not receive significant focus in treaty-based efforts to limit climate change. But the ICJ Advisory Opinion explicitly noted that fossil fuel licencing and production “may constitute an internationally wrongful act attributable to that State.” (para. 427) The ICJ also clarified that States’ obligation to mitigate domestic emissions—by setting and implementing Nationally Determined Contributions—is not their only potential source of liability. (para. 314) Ultimately, States can be liable for climate harms that are attributable to their actions, or the actions of private actors within their jurisdiction and control. (ICJ AO, para. 314) This includes harm from oil and gas that is dug up domestically, then exported and burned abroad. (North Sea Fields, p. 43)

In People v. Arctic Oil, the ECtHR found a “sufficiently close link” between State approval of new fossil fuel projects and human rights harms. (para. 299) Attribution science strengthens this link: recent research connects individual fossil fuel projects to measurable climate harms, such as excess heat-related mortality. Potential future “market substitution” of the emissions from foregone projects is irrelevant to this analysis. (North Sea Fields, p. 32)

States have stringent due diligence obligations to prevent harm to the climate system, protect human rights and conserve reservoirs of GHG emissions

If new fossil fuel projects cause harm, does State action facilitating that harm violate international law? Three obligations are relevant here.

First, as articulated by the ICJ, States have a duty under customary international law to prevent significant harm to the climate system and other parts of the environment. (ICJ AO, paras. 272-300) Second, States have duties under international treaties to respect, protect, and fulfil human rights. (ICJ AO, paras. 369-404) These customary and treaty obligations are intertwined: the ICJ noted “full enjoyment of human rights cannot be ensured without the protection of the climate system”. (ICJ AO, para 403). Third, States listed in Annex I of the UNFCCC have an obligation to “conserve and enhance, as appropriate […] reservoirs of greenhouse gases”. (Paris Agreement, art. 5(1); UNFCCC, art. 4(1)) “Reservoirs” are defined to include fossil fuel deposits, which are “precursors” of GHG emissions. (UNFCCC Article 1(7); UNFCCC Glossary)

States’ compliance with these obligations does not require the achievement of a defined outcome. Instead, compliance depends on whether States have exercised stringent due diligence in seeking to fulfil them. The standard is stringent, given the severity and urgency of the risks involved. (ICJ AO, para. 137; ITLOS AO, paras. 243, 256; IACtHR AO, paras. 233-236)

 Due diligence is not subjective, but can be “determined objectively” through an assessment of multiple factors. (ICJ AO, para. 300, ITLOS, para. 257) These include the degree to which a State has (i) taken “all appropriate measures” to fulfil their substantive obligations, (ii) exercised “best efforts”, (iii) acted in conformity with the severity and urgency of the risks, (iv) the best available science, (v) the precautionary principle, and (vi) relevant international standards, (vii) all taking into account the State’s differentiated level of historical climate responsibility and capacity to act (CBDR-RC).

New fossil fuel projects are incompatible with limiting global temperatures to 1.5ºC (or 2ºC)

The 1.5ºC temperature limit grounds the due diligence standard in the climate context. The ICJ described this limit as the “primary” goal of the climate treaties, in line with the best available science. (ICJ AO, paras. 197, 224) The 1.5°C limit also informs the conduct required of States in fulfilling their other obligations, consistent with the interpretative principle of systemic integration.

With every increment of warming beyond 1.5ºC, risks to the climate system compound and accelerate unpredictably, including the risk that foundational sub-components of the climate system will pass tipping points and irreversibly unravel. (IPCC, B)

New fossil fuels are incompatible with limiting global temperatures to 1.5ºC. That’s because, globally, there are vast reserves contained in projects that are already developed or under-construction—so vast, that if we burned them all we would exceed the “budget” of carbon dioxide that we can globally emit while keeping temperatures to even 2ºC (IPCC, B.5.3). The global 1.5ºC carbon budget is almost depleted: at current rates of emissions, there is a 1-in-2 chance it will be gone within three years. Researchers estimate that, to stay below 1.5ºC, approximately 60% of fossil fuels in existing projects must therefore remain in the ground.

Under the precautionary principle, States must assume that all reserves in newly developed fossil fuel projects will end up as atmospheric emissions, not offset by relevant technologies. (ICJ AO, para. 158; People v. Arctic Oil, para. 294). As the UK Supreme Court has noted, “[t]he whole purpose of extracting fossil fuels is to make hydrocarbons available for combustion,” so there is “virtual certainty” that extracted fuels will contribute to global warming. Technology-based CDR methods currently remove a minuscule (<0.01%) amount of global emissions, and their capacity to scale remains highly speculative. The assumption that projects will be closed early, leaving developed reserves unburned, is also highly speculative given the strong incentives for businesses, unions and governments to protect their vested economic interests in ongoing operations.

Domestic courts have already affirmed that the 1.5ºC carbon budget grounds the due diligence standard. In North Sea Fields, the appeals court required that, before any new approval is granted, Norway assess the global combustion emissions both from the proposed projects, and from all its operational projects on the continental shelf, against the 1.5ºC budget. (p. 43)

New fossil fuel projects are incompatible with States’ “best efforts”

Stringent due diligence requires that States, in accordance with their respective capacities and responsibilities, exercise best efforts to fulfil their substantive obligations by using all means at their disposal. These factors also weigh against the legality of approval of new fossil fuels.

Recent social and political science research indicates that new fossil fuel projects are not necessary—instead, a ban would yield economic and social benefits. First, new fossil fuel projects are not required to meet global energy needs. This is supported by IPCC scenario analysis of feasible pathways consistent with limiting future warming to 1.5ºC and with thresholds for CDR feasibility and sustainability, under which global energy needs are met – none of which include new fossil fuel developments.

Second, new fossil fuel projects are cost-inefficient. A future with no new fossil fuel projects is cheaper for households than alternative trajectories. (IEA, pp. 51, 346) Such projects foreclose less risky investments in green energy by creating carbon lock-in and stranded assets. (UNEP, p. 19; IPCC, C.4.4)) Meanwhile, the associated profits almost exclusively flow to a small group of wealthy owners. The global welfare gains from a ban on new exploration are estimated in the trillions. These gains stem not just from reduced warming, but also from avoiding the vast health burden that fossil fuel projects directly cause through toxic pollution and biodiversity loss.

For wealthy states, the principle of CBDR-RC obliges them to phase down fossil fuels faster than other countries, and provide them with technical assistance for mitigation. (AO, para. 292) Meanwhile, even for countries with the least responsibility and capability, CBDR-RC cannot justify actions that are substantively incompatible with due diligence. (ICJ AO, paras. 291; Boshoff & Damtew)

Conclusion: what lies ahead

The planet will keep heating up and the climate will keep breaking down until we phase out fossil fuels. And our vast existing reserves of those fuels well exceed what we can safely burn. In light of these facts, State approval of new fossil fuel projects cannot be reconciled with the legal obligation to act with stringent due diligence to appropriately conserve reservoirs of fossil fuels, to prevent significant harm to the climate, and to respect, ensure and protect human rights.

It remains to be seen how domestic courts will approach this substantive question. Such courts traditionally afford governments a degree of deference in how they implement their international and regional obligations—known in the European context as the “margin of appreciation”—but that deference is not without limits. The ECtHR held in KlimaSeniorinnen v. Switzerland that States have a narrowed margin of appreciation with respect to the “requisite aims” of climate action, which must be set with due regard to the global carbon budget, but they have broad flexibility on the “choice of means” to achieve those aims. (paras. 543, 550(a)) The margin of appreciation does not permit outcomes that are fundamentally incompatible with the human rights protection granted under the Convention: best available science shows that new fossil fuel projects are inconsistent with effective climate action, so cannot be treated as a discretionary policy choice.

Last, the legal framework limiting State support for fossil fuels that is developing through domestic, regional and international climate jurisprudence has relevance well beyond courtrooms. It has clear implications for international advocacy and diplomacy, including the Fossil Fuel Non Proliferation Treaty, and the First International Conference on the Just Transition Away from Fossil Fuels that will take place in Colombia in April 2026.

The blog has been amended to clarify that the subset of IPCC scenarios analysed by Green et al. includes C1 scenarios that comply with IPCC feasibility and sustainability thresholds for CDR. The blog originally described this subset as including ‘feasible’ C1 pathways.