Private enforcement of climate law
Public enforcement in law is the process by which government agencies investigate and prosecute potential wrongdoing. Private enforcement is a less clear-cut concept; it can refer to any action brought to court by a private party. [1] Private enforcement, therefore, is the process that allows citizens to hold emitters accountable. Individuals, or civil society organisations (often environmental nonprofit organisations) take governments or corporations to court, hoping to force these defendants to take action reducing their emissions, or to pay damages. [2]
It’s useful to separate “horizontal” climate action, which targets major emitters on a case-by-case and retroactive basis, from “vertical” climate action, which concerns insufficient state policy or enforcement, and can lead to change in national legislation. [3]
The precedent principle in common law
In common law jurisdictions, the judge must follow the decisions of higher courts (so called “binding precedents”) when presented with a similar case. If judges turn to previously-issued opinions to inform their decision-making, a single successful suit where an emitter is found liable for environmental harms can lead to the judge finding in favour of the plaintiff. When a private lawyer brings a lawsuit against an emitter, they can claim it to be in the public interest. In this context, they may be called a “private attorney general”. [4]
The private attorney general has been a key principle furthering environmental justice across many national jurisdictions; individual lawyers and civil society actors have successfully filed litigation to protect civil or consumer rights. [5] In public interest cases in some jurisdictions – including the United States – the claimant is typically entitled to recover their legal fees if they win, which can remove a major deterrent to pursual of such cases. [6] A similar provision exists in international law, under the Aarhus Convention, which requires that access to environmental justice not be prohibitively expensive. [7], thus allowing individuals to sue the government, or large corporations, without the risk of incurring financial burdens.
Empowering citizens to take action
Private enforcement has been a valuable tool permitting civil society to fight climate change for decades, with a landmark U.S. case in 2005 – “Comer v. Murphy Oil U.S.A” – often cited as the first attempt at using common-law tort legislation to bring emitters to justice. [8] A group of citizens sued several fossil fuel companies, arguing that the companies’ emissions had intensified Hurricane Katrina and contributed to the damage to their property. [9] After the initial dismissal, a 2007 Supreme Court precedent recognizing a causal link between fossil‑fuel emissions and global warming allowed the case to be successfully appealed in 2009. The appeal established two important principles: first, that private citizens could bring state common‑law tort claims; and second, that plaintiffs only needed to show that a company’s emissions contributed to the harm — not that they were the sole cause. [10]
After this, a number of similar suits were brought across the world, often on behalf of environmental NGOs or individual citizens, based on claims alleging harm done to the body, to the health, or to property. [11] On 26 May 2021, Dutch NGO Milieudefensie successfully brought a landmark class action suit against Shell, on behalf of the collective public. [12] Combining Shell’s corporate policy with the human rights principles affirmed by the UN Charter, the Dutch court found that Shell had an obligation to reduce its Scope 3 emissions. [13] In common law systems, each successful case sets a valuable precedent, allowing future would-be plaintiffs to push courts further in their recognition of harms for which emitters are liable. The 2021 case set the precedent that under tort law private corporations have a duty of care that is violated by causing environmental harms. [14]
The financial protections offered to claimants in these public interest suits have allowed private enforcement to emerge as a viable strategy for holding polluters to account when governments cannot – both nationally and internationally. For instance, Milieudefensie’s case was heard in a national court, but the plaintiffs demands included an international emissions reduction. [15]Another example is the long‑running lawsuit brought on behalf of Peruvian farmer Luciano Lliuya against German energy company RWE. His appeal was dismissed by the German high court in 2025 due to insufficient evidence of the specific property damage he claimed. [16] However, the court did not reject the broader idea that German companies could be held liable for climate‑related harms occurring outside Germany.
[17, 18] The ruling left open the possibility that emitters may have a duty to take preventive measures or compensate affected communities in other jurisdictions.Implicitly, the ruling a hypothetical an obligation for emitters to take “preventive” action, or otherwise compensate affected parties. [19]
Conclusions
Recent advisory opinions issued by the International Courts of Justice and Inter-American Court of Human Rights suggest that private enforcement as a legal phenomenon will continue to gain momentum in years to come. [20, 21, 22, 23, 24]
