Climate Lawsuits Hang on One Procedural Gate at the Supreme Court

The Gateway Case No One Is Calling What It Is

The Supreme Court is about to decide whether a single city in Colorado can sue Exxon Mobil and Suncor Energy for the costs of climate change. But describing this case as a straightforward dispute between a municipality and two oil companies misses what is actually happening.

What the Court is hearing is a procedural gateway — a threshold question that will determine whether hundreds of similar lawsuits filed by states and local governments across the country can proceed at all. The case, Suncor Energy v. County Commissioners of Boulder County, returns to the bench this Monday as the first major case of the Court’s new term. It sounds like a narrow jurisdictional matter. It is not.

The outcome will shape the legal architecture of climate accountability for decades.

How We Got Here

Boulder filed its lawsuit in 2018, alleging that Exxon and Suncor’s production and deceptive marketing of fossil fuels contributed to the greenhouse gas buildup driving extreme heat, wildfires, and ecosystem damage in the region. The city and county raised five state-law claims. They did not sue over emissions — they sued over marketing and production decisions that they argue mislead consumers and regulators about the risks of fossil fuel use.

Exxon and Suncor tried to move the case to federal court. They failed. They then asked the Boulder County District Court to dismiss it, arguing that federal law — specifically the Clean Air Act — foreclosed their state-law claims. That request was denied. The Colorado Supreme Court sided with Boulder. The energy companies appealed to the United States Supreme Court.

Now the high Court faces two questions. First: does it even have jurisdiction to review the Colorado Supreme Court’s decision? Second, if it does: does the Clean Air Act preempt Boulder’s state-law claims?

Only eight justices will participate. Justice Samuel Alito recused himself, though no reason was given. His 2025 financial disclosures show individual holdings in ConocoPhillips and Phillips 66 — not Exxon or Suncor directly. An eight-justice Court dividing 4-4 is a real possibility, and a tie would leave the Colorado Supreme Court’s ruling intact, allowing Boulder’s case to proceed to trial.

The Energy Companies’ Argument — and Its Limits

Exxon and Suncor’s legal case rests on two pillars. The first is the Clean Air Act. Their lawyers argue that the statute occupies the field of air pollution regulation and that allowing state tort claims based on greenhouse gas emissions would create a patchwork of conflicting climate policies across fifty states and tens of thousands of municipalities. “It’s a national problem, so it requires a national solution,” said Michael Williams, West Virginia’s solicitor general, who is among twenty-six states backing the energy companies.

The second pillar is foreign affairs. The Trump administration, which has filed support briefs with Exxon and Suncor, warns that Boulder’s suit creates “needless diplomatic friction” with countries where the companies operate. Allowing state courts to adjudicate liabilities tied to emissions produced abroad, the administration argues, undermines the executive branch’s control over international diplomacy on climate.

Both arguments have structural weaknesses.

The Clean Air Act regulates emissions from specific sources. It does not regulate the upstream production and marketing of fossil fuels — which is precisely what Boulder is suing over. Jonathan Adler, a law professor at William & Mary who filed a brief supporting Boulder, noted that the city is not asking courts to set climate policy. It is asking energy companies to bear the costs of allegedly deceptive conduct. “Avoiding liability would not require reducing emissions at all — only telling the truth,” his brief argued.

The foreign affairs claim is more fragile still. As Adler pointed out, the Trump administration has withdrawn from international climate agreements that once provided diplomatic frameworks for addressing greenhouse gas emissions. The argument that state court litigation on climate disruption somehow interferes with diplomatic channels rings hollow when the executive branch has systematically dismantled those channels. “If there was an actual conflict between an actual treaty, of course that could preempt state law,” Adler said. “But we don’t even have that.”

Who Wins, Who Loses, and What Happens Next

If the Supreme Court dismisses the case for lack of jurisdiction, the Colorado Supreme Court’s decision stands and Boulder’s lawsuit moves forward. That outcome would preserve a precedent that other municipalities can cite. Dozens of similar cases filed in state courts from San Francisco to New Orleans to Hartford would remain viable.

If the Court reaches the merits and rules that the Clean Air Act preempts Boulder’s claims, it would effectively shut down the entire category of municipal climate-damage litigation. Energy companies would gain a federal shield against state-law tort claims tied to their production and marketing activities. The precedent would extend beyond Colorado — it would apply to every state court case seeking damages for climate harms attributed to fossil fuel companies.

There is a third possibility that deserves attention. The Court could rule narrowly, finding that while the Clean Air Act does not preempt all state-law claims related to climate change, it bars claims that attempt to regulate interstate or global emissions. That would leave Boulder’s marketing-focused claims intact while blocking future suits that explicitly target emission reductions through tort law. The line between “suing over deceptive marketing” and “suing over emissions” is thin, and lower courts would spend years parsing it.

Congress could resolve the uncertainty. Adler noted that lawmakers have done this before — the 2005 law shielding gun manufacturers from civil lawsuits for criminal misuse of their products is a direct parallel. If Congress decides that climate liability suits represent judicial overreach or unwanted pressure on energy companies, it has the tools to address that. But Congress has not moved on this, and the current political dynamics make legislative action unlikely in the near term.

The Global Implications

This is not only an American story. Climate litigation is accelerating worldwide. Municipalities in Europe, Asia, and Latin America are watching closely to see whether U.S. state courts remain open forums for climate damage claims. A Supreme Court ruling that preemptively blocks such suits would send a signal to litigants and corporations globally.

Conversely, a ruling that allows Boulder’s case to proceed would reinforce the growing trend of subnational actors using domestic courts to address global problems that international negotiations have failed to solve. It would legitimize a legal strategy that climate activists have been developing for years: hold the producers accountable for the consequences of what they sell.

A decision is expected by summer 2027. Whatever the Court decides, the procedural question it faces first — whether it has the authority to hear this case at all — will determine the scope of that decision’s reach. The gateway is narrow. What passes through it will define climate litigation for a generation.