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Cities and states are taking climate disputes to court to seek money for alleged local harms, challenge federal climate rules, or defend laws that require energy companies to pay. These are different kinds of cases—not one nationwide lawsuit—and each raises a different question about the boundary between state and federal power.
Why are cities suing fossil fuel companies over climate change?
Some local governments say climate change has caused or will cause costs within their communities and are seeking damages from fossil fuel companies under state law. They argue that state courts can consider injuries in their state even when the fuels were produced elsewhere. The companies, in turn, argue that state-court lawsuits are an improper way to address a global problem.
The legal dispute is not simply whether climate change causes harm. It also concerns which courts may hear these claims, whether state-law claims can proceed in the face of federal authority, and what remedies a court could award. The plaintiffs’ allegations and requested damages are not findings that the companies are liable.
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What is the Boulder climate lawsuit?
The claims and the companies’ challenge
Boulder County and the City of Boulder sued fossil fuel companies in 2018, seeking damages for alleged climate-related harms. As the Associated Press reported, Boulder’s position is that state lawsuits can address damage within Colorado even if fossil fuels were produced elsewhere. The companies argue that the dispute belongs in a different legal framework because greenhouse gas emissions and their effects cross state lines.
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Why the Supreme Court’s procedural question matters
The U.S. Supreme Court heard argument on October 5, 2026, on the companies’ appeal. A threshold issue is whether the Court may review the case before Colorado’s courts have completed their proceedings. Colorado Attorney General Phil Weiser said the Court had agreed to hear the appeal at that stage and directed the parties to address its authority to do so. A coalition brief led by Colorado urges respect for the state-court process; Weiser put the principle this way: “Our federal system depends on state and federal courts each fulfilling their proper role.”
At argument, Chief Justice John Roberts asked, “Presumably, if you prevail, the next day, a municipality in every single state will file a lawsuit.” Justice Ketanji Brown Jackson asked, “Why shouldn’t we wait and hear all of these claims once the state courts are done?” Those questions show the concerns being tested, not how the Court will rule. The sources available as of October 7, 2026, do not establish a Supreme Court decision in the case.
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Why are states and cities suing the EPA?
Other climate cases target federal agency action rather than companies. These are petitions for judicial review: the governments ask a court to examine an agency’s action and grant specified relief. A petition’s claims and requested remedy are not a court ruling.
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Challenge to the Endangerment Finding rescission
The California attorney general reported that on March 19, 2026, a coalition of 25 attorneys general, Pennsylvania’s governor, and 10 cities and counties petitioned the D.C. Circuit to challenge EPA’s rescission of the Endangerment Finding. California describes that finding as EPA’s formal acknowledgment that greenhouse gas emissions from motor vehicles contribute to air pollution that drives climate change and endangers public health and welfare. The coalition asks the court to vacate the rescission and restore vehicle greenhouse gas standards. Those are the petitioners’ requested remedies, not relief the court is reported to have granted.
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Challenge to a rule affecting HFC phase-down requirements
Delaware reported that 19 attorneys general and one city challenged an EPA rule affecting requirements to phase down hydrofluorocarbons (HFCs) in commercial equipment. The coalition argues that the rule conflicts with the American Innovation and Manufacturing Act and is inadequately justified. Delaware’s 2026 release says HFCs can have up to 10,000 times the warming potency of an equivalent amount of carbon dioxide; that figure is the state’s reported characterization.
What is a climate superfund law?
A climate superfund law seeks payments from energy companies for climate-related costs. It is a state statute, so lawsuits over these laws raise a different question from a local government’s damages case: whether a state may impose the law’s financial obligations when the federal government argues that the statute is preempted by federal law or is unconstitutional.
In a May 2025 announcement, the U.S. Department of Justice (DOJ) said New York’s 2024 Climate Change Superfund Act sought $75 billion from energy companies and Vermont’s law sought an unspecified amount. DOJ challenged the New York and Vermont laws and separately sued to prevent anticipated climate-damages suits by Hawaii and Michigan. The claims that these laws and suits are preempted or unconstitutional are DOJ’s legal positions.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How do the main climate cases differ?
| Dispute | Plaintiff or challenger | Defendant or target | Claim and requested action | Court or stage described |
|---|---|---|---|---|
| Boulder damages suit | Boulder County and the City of Boulder | Fossil fuel companies | State-law claims seeking damages for alleged climate harms in Colorado | The Supreme Court heard argument October 5, 2026, on the companies’ appeal, including whether it may review the case before Colorado’s courts finish proceedings; no decision is established in the sources available as of October 7, 2026. |
| Endangerment Finding challenge | Coalition reported by California: 25 attorneys general, Pennsylvania’s governor, and 10 cities and counties | EPA action rescinding the Endangerment Finding | Petition asks the D.C. Circuit to vacate the rescission and restore vehicle greenhouse gas standards | Petition reported March 19, 2026; the source describes the coalition’s request, not a ruling. |
| HFC rule challenge | Coalition reported by Delaware: 19 attorneys general and one city | EPA rule affecting HFC phase-down requirements | Coalition argues the rule conflicts with the American Innovation and Manufacturing Act and is inadequately justified | Delaware reported the challenge; the source describes the coalition’s claims, not a ruling. |
| New York climate superfund challenge | U.S. Department of Justice challenging the state law | New York’s Climate Change Superfund Act | DOJ alleged the law was preempted or unconstitutional; the 2024 law sought $75 billion from energy companies, according to DOJ | DOJ reported on September 30, 2026, that federal district courts invalidated the law and enjoined the penalties. |
The comparisons show why “climate lawsuit” is an umbrella label rather than a single legal theory: the plaintiff, target, requested remedy, court, and asserted role of state and federal law all change from case to case.
What is at stake in these courtroom fights?
The central conflict is over who can make policy or award remedies when greenhouse gas emissions and alleged harms cross state lines. Local governments and states argue that their laws and courts can address particular harms or review agency actions. Companies and federal officials challenge some of those efforts by invoking federal authority, jurisdiction, preemption, or constitutional limits.
The procedural stage matters as much as the underlying policy dispute. A petition asks a court to act; an argument allows judges to test positions; and a ruling resolves particular legal questions at a particular stage. The Supreme Court’s Boulder argument, the petitions challenging EPA actions, and DOJ’s account of the New York district court rulings therefore should not be treated as interchangeable outcomes.
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