The United States Supreme Court has agreed to review the Colorado Supreme Court’s decision in City and County of Boulder v. Suncor Energy (U.S.A.) Inc., which allowed the municipality’s climate change-related tort claims against Exxon Mobil and Suncor Energy to proceed. The Supreme Court’s review of this case will likely have broad ramifications for states’ ability to pursue reparations from fossil fuel companies for carbon emissions. The Court’s grant of certiorari follows its denial of a similar petition last year, which sought review of the Hawaii Supreme Court’s decision to allow Honolulu’s state-law climate tort action to proceed.
In its state court complaint, Boulder asserted state-law nuisance, trespass, unjust enrichment, misrepresentation, and civil conspiracy claims, seeking damages against Exxon and Suncor for their contributions to localized adverse effects of climate change. The municipality alleges that Exxon and Suncor misled the public regarding the adverse effects of fossil fuel emissions to maintain demand for their products.
Exxon and Suncor maintain that Boulder is seeking damages for cumulative impacts of global emissions without congressional authorization for such extraterritorial state law claims. Before the Colorado Supreme Court, Exxon and Suncor asserted that federal common law governs interstate emissions disputes because climate change is a “uniquely federal interest.”
In May 2025, the Colorado Supreme Court affirmed a lower court ruling that the suit could proceed. The court rejected the defendants’ invocation of federal common law, reasoning that the U.S. Supreme Court’s ruling in American Electric Power v. Connecticut held that the Clean Air Act (CAA) displaced federal common law previously allowing states to sue each other over air pollution. The issue before the Colorado Supreme Court was whether the Clean Air Act preempts Colorado’s state law claims. The court held that the CAA does not preempt Boulder’s state law claims, as Congress has not occupied the field of emissions regulation because “states retain regulatory authority to implement, maintain, and enforce CAA emissions standards through state implementation plans.” According to the court, the defendants failed to demonstrate that Colorado tort law directly conflicts with the CAA or frustrates the CAA’s purposes.
Suncor and Exxon petitioned for certiorari before the U.S. Supreme Court. The petition notes that, in yet another state-law climate tort action brought by the City of Baltimore, the Trump administration has taken a position contrary to the Hawaii and Colorado Supreme Court decisions, asserting that federal law precludes the City of Baltimore’s state law climate tort claims in a similar action. The petitioners also pointed to the Second Circuit’s decision in City of New York v. Chevron Corp., where that court concluded that it was “too strange to seriously contemplate” that state law is “presumptively competent” to provide a cause of action with respect to interstate pollution issues. 993 F.3d 81, 99 (2021). According to the energy companies, the Colorado Supreme Court’s decision effectively allows the municipality to “make energy policy for the entire country.” In opposing the petition, Boulder argued in part that the Court lacks jurisdiction to hear an interlocutory appeal from the Colorado Supreme Court allowing the action to proceed.
On Monday, February 23, 2026, the U.S. Supreme Court granted Suncor and Exxon’s petition for certiorari. The Court specifically requested that the parties brief whether the Court has statutory and Article III jurisdiction to hear the case.
In addition to various other tort-based climate suits on grounds similar to Boulder, the Supreme Court’s decision in this case will directly affect currently pending challenges to several states’ Climate Superfund laws. Those challenges in Vermont and New York argue that the Clean Air Act preempts the Climate Superfund laws, precluding states from creating new causes of action for climate-based damages against fossil fuel companies. For more on those cases, click here.
Additionally, EPA’s rescission of its landmark endangerment finding regarding greenhouse gas emissions may further complicate the petitioners’ preemption arguments. The federal government’s rollback of authority to regulate greenhouse gas emissions could support Boulder’s argument that the CAA does not preempt state laws or lawsuits pertaining to injuries caused by those emissions. Given that the parties’ briefing before the Colorado Supreme Court and in connection with the petition for certiorari occurred prior to the endangerment finding repeal, the parties’ arguments on the merits before the U.S. Supreme Court may help shed further light on this issue.
This article was written by associate Louis Dodge. To learn more about how this historic Supreme Court decision, Louis can be reached at ldodge@lssh-law.com.