NACo Legal Advocacy: Suncor Energy v. Boulder County
Key Takeaways
On August 3, NACo joined the Local Government Legal Center (LGLC), the National League of Cities and the International Municipal Lawyers Association in an amicus brief before the U.S. Supreme Court in Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County (No. 25-170). The case asks whether federal law prevents local governments from pursuing state-law claims seeking damages for costs associated with climate-related impacts.
The case has broader implications for counties because the petitioners are asking the Court to adopt federal preemption principles that could affect when local governments may use state law to recover costs from private parties in other types of litigation.
Background
In 2018, Boulder County and the City of Boulder sued Suncor Energy and Exxon Mobil in Colorado state court. The local governments allege that the companies' production and marketing of fossil fuels, along with alleged misrepresentations about their impacts, contributed to climate-related harms that have imposed costs on local taxpayers.
Boulder is seeking monetary damages under Colorado law for costs associated with issues including wildfire response, flood infrastructure, drought management and damage to public property. The lawsuit does not ask the court to establish emissions standards or stop fossil fuel production.
The Colorado Supreme Court allowed the claims to proceed in May 2025, finding that federal law did not prevent Boulder from pursuing its state-law claims. The Court granted certiorari on February 23, 2026 to hear the case to consider whether federal law precludes state law tort claims brought by local governments to recover the local costs of climate change impacts from fossil fuel producers beyond state lines.
County Nexus
The danger to counties from ruling in favor of the petitioner is not related to climate policy, but rather it is in the legal architecture petitioners are asking the Court to adopt. which include two key principles that, if adopted, would circumvent how local governments can file suit for damages in state court for damages beyond state lines:
- Constitutional Preclusion: State law cannot reach any conduct with significant "interstate aspects" when the federal interest is strong, even where Congress has not expressly preempted state law. State courts can hear claims only to the extent Congress affirmatively authorizes state-law remedies.
- Silent Displacement: When federal common law is displaced by a federal statute, state law is also silently displaced unless Congress clearly says otherwise. This inverts the ordinary presumption against preemption.
At its core, this case is about whether counties retain access to their own state courts to share those costs with private parties whose alleged conduct contributed to the harm. Suncor argues, in part, that state law cannot be used to address claims involving interstate and international greenhouse gas emissions because of the federal government's role in regulating interstate pollution and foreign affairs. The companies also argue that the federal Clean Air Act (Pub. L. 88-206, 77 Stat. 392) preempts Boulder's claims. Boulder disputes those arguments and maintains that its lawsuit seeks compensation for local injuries rather than regulation of emissions.
Counties have long relied on state common law, including public nuisance and trespass claims, to address harms occurring within their jurisdictions and recover costs borne by local governments and taxpayers. The amicus brief argues that neither the Clean Air Act nor broader constitutional principles should categorically prevent Boulder from pursuing those claims.
Counties rely on state law in litigation seeking to recover public costs associated with issues such as the opioid epidemic and per- and polyfluoroalkyl substances (PFAS) contamination. The legal principles adopted by the Court in this case could therefore influence how federal preemption defenses are raised in other cases involving nationally distributed products or conduct with effects across state lines.
NACo Advocacy
NACo will be joining the Local Government Legal Center (LGLC) in filing an amicus brief in support of Boulder County to educate the Court on how counties rely on state tort law, public nuisance doctrines and consumer protection statutes as complementary tools to federal enforcement. The brief will emphasize the need to preserve state power, maintain limits on preemption of counties and ensure the proper use of federal laws. Clarifying these limits is critical to protecting federalism and preserving counties' ability to protect their residents.
Current Status
The Court has scheduled oral argument in Suncor Energy v. Boulder County for October 5.
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