Climate Change and State Authority: Potential Broad Implications of the Supreme Court's Grant of Certiorari in Suncor Energy, Inc v. Commissioners of Boulder County

Takeaways

• The U.S. Supreme Court has granted certiorari in Suncor Energy, Inc., et al. v. Commissioners of Boulder County, et al., No. 25-170, a case arising from climate change tort claims brought by Boulder County and the City of Boulder, Colorado.
• The Court will review whether federal law bars state-law claims seeking damages for injuries allegedly caused by the effects of interstate and international greenhouse-gas (GHG) emissions.
• The Court's cert grant raises the possibility that the Court may not reach the merits. In granting review, the Court is requiring the parties to address whether it has statutory and Article III jurisdiction.
• This is the first time the Court will consider whether federal law bars climate damages lawsuits, and a merits decision could affect dozens of similar state and local lawsuits nationwide against energy companies alleging climate-change harms. The decision could also have broader implications for State laws, such as State “climate Superfund” laws that seek to recover for climate-related harms. The case could therefore be of great significance.

Background

Boulder County and the City of Boulder filed suit against Suncor Energy U.S.A. Inc. (and an affiliate) and Exxon Mobil Inc. asserting Colorado statutory and common-law causes of action—including public nuisance, private nuisance, trespass, unjust enrichment, and civil conspiracy—and seeking damages tied to alleged climate-change impacts. In May 2025, the Colorado Supreme Court ruled that federal law did not preempt Boulder's state-law tort claims and allowed them to proceed.

Suncor and Exxon Mobil sought certiorari, arguing that claims seeking to address interstate and international GHG emissions were barred by federal law, and that the Colorado Supreme Court's ruling was inconsistent with a decision of the Second Circuit and other decisions of federal courts of appeals. Multiple amici filed briefs supporting certiorari, including a (very unusual) uninvited amicus brief from the United States. The Supreme Court granted certiorari and directed that the parties also brief “whether this Court has statutory and Article III jurisdiction to hear this case.”

The Court is expected to hear arguments in the fall of 2026 and issue a decision before July 2027.

Analysis

Jurisdiction 

The Court directed the parties to brief jurisdictional issues that could prevent the Court from addressing preemption. Boulder's opposition to certiorari argued that the Colorado Supreme Court's decision was interlocutory and thus not a “final judgment” that the Supreme Court may review. Boulder also asserted that the case presents novel Article III standing issues because it could not have brought the case in federal court in the first instance.

Scope of Permissible State-Law Claims

If the Court reaches the merits, it will determine the extent to which plaintiffs can use state-law claims to redress harms from climate change. Suncor's petition for certiorari argues that Boulder's tort claims are barred because they properly arise under federal common law and are displaced by the Clean Air Act. In the alternative, Suncor argues the Clean Air Act restricts the application of state-law claims to interstate pollution. To the extent Boulder's claim is directed at international emissions, Suncor argues that “foreign-policy principles” bar such claims. 

Preemption of State and Local Law 

Some commenters argue that EPA's recent decision to rescind the mobile source Endangerment Finding under Section 202(a)(1) of the Act opens the door to broader state authority and weakens arguments—like Suncor's—that federal law preempts state tort suits alleging climate harms. B&D has issued a separate client alert on the rescission of the Endangerment Finding. EPA has not yet rescinded the endangerment finding under CAA Section 111 relating to stationary sources or the associated regulations, so those existing EPA actions continue to have preemptive effect. As to mobile sources, EPA's rescission of the endangerment finding expressly states that it “does not impact Federal preemption for motor vehicle and engine emission standards under CAA section 209(a) or under EPCA and EISA.” EPA's response to comments document also discusses that issue in some detail and asserts the position that “preemption under CAA section 209(a) [is] broader than the scope of authority to regulate” under the statute “or the way we choose to exercise it.” 

Potential Implications 

Should the Court reach the merits in the case, the Court's decision could be of great significance, given the number of pending cases seeking redress for harms associated with climate change. Suncor's cert petition said that the Colorado Supreme Court's decision “perpetuates an unsustainable and chaotic patchwork of regulation of interstate and international emissions” and “threatens one of this Nation's most critical industries.” The legal theories Suncor asserts are broad and could extend beyond lawsuits to other actions by States and local governments, such as efforts by States to address harms associated with climate change through so-called “climate Superfund” legislation.

Interested businesses and other stakeholders should monitor the Suncor case, particularly if they are involved in litigation or other matters that could be affected by the Court's eventual resolution of the case, and consider whether amicus participation is warranted. 

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