Attorney General Phil Weiser defends state courts’ role in climate case before U.S. Supreme Court

Aug. 3, 2026 (DENVER) – Attorney General Phil Weiser today co-led a multistate coalition of attorneys general in filing a court brief in the U.S. Supreme Court in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County, urging the court to follow longstanding jurisdictional rules and preserve the role of state courts in resolving state common law claims.

The case stems from a lawsuit filed by Boulder County and the City of Boulder against several fossil fuel companies seeking damages for alleged harms related to climate change. The companies asked the Supreme Court to review the case before Colorado’s courts have finished considering it. In addition to agreeing to hear the appeal, the Supreme Court directed the parties to address whether it has the authority to hear the case at this stage of the litigation.

“Our federal system depends on state and federal courts each fulfilling their proper role,” said Attorney General Weiser. “This case involves the basic question whether Colorado courts can consider common law claims that fossil fuel companies engaged in wrongful behavior that contributed to climate change. At this stage of the case, it would be an overreach and improper for the Supreme Court to prevent Colorado courts from considering the merits of this litigation.”

The coalition contends that the Supreme Court should first determine whether it has the authority to hear the case. If it does not, the lawsuit should continue in Colorado’s courts. The attorneys general say following that process protects the longstanding role of state courts.

The attorneys general also argue that the court’s decision could affect far more than this case. States across the country rely on their courts to decide a range of state common law claims, and the coalition warns that allowing federal courts to intervene before state court proceedings are complete and decided on their merits would impact a range of cases well beyond the climate litigation brought here.

The brief further explains that states should not lose their authority to apply state law simply because a case involves issues that cross state lines. The attorneys general say the Constitution does not automatically prevent states from hearing these claims.

Finally, the coalition notes that state courts already have well-established legal rules for determining whether claims should proceed. Those decisions, the attorneys general say, should be made through the normal judicial process rather than through a broad new federal rule that prevents state law claims from proceeding in state courts.

Colorado Attorney General Weiser co-led the coalition with California Attorney General Rob Bonta. The brief was joined by the attorneys general of Arizona, Connecticut, Delaware, the District of Columbia, Hawai‘I, Illinois, Maine, Maryland, Massachusetts, Michigan, Nevada, New Jersey, New York, Oregon, Rhode Island, Vermont, and Washington.

Read the states’ amicus brief in Suncor Energy v. County Commissioners of Boulder County (PDF).

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Media Contact:
Lawrence Pacheco
Chief Communications Officer
(720) 508-6553 office
lawrence.pacheco@coag.gov