The U.S. Supreme Court on Monday accepted an appeal from ExxonMobil and Suncor Energy challenging a Colorado lawsuit that accuses the companies of contributing to climate change and seeks unspecified monetary relief to cover costs the city and county of Boulder say they have incurred in responding to climate impacts.
The companies are appealing a lower-court ruling that allowed the Boulder litigation to move forward. The suit, originally filed in 2018, alleges violations of state law and requests compensation for a range of expenses Boulder government officials say are associated with mitigating the effects of climate change.
Plaintiffs have pointed to a variety of costs they attribute to climate-related impacts, asking that the oil companies cover past and future expenditures tied to infrastructure repairs, environmental harm, emergency management and consequences for public health. In their complaint, Boulder officials also accused the U.S.-based Exxon and Canada-based Suncor of misleading the public about how their products contribute to worsening climate conditions while continuing to profit from fossil fuel sales. Both companies deny any wrongdoing.
In urging dismissal at the lower-court level, the oil companies argued that Boulder’s lawsuit would unlawfully intrude on federal regulation of greenhouse gas emissions under the Clean Air Act. The Colorado Supreme Court rejected the companies’ effort to halt the case in May 2025, a decision that prompted the appeal to the U.S. Supreme Court. The appeal has received support from the administration of President Donald Trump.
This Boulder case is one among dozens of climate-related lawsuits brought by U.S. jurisdictions against firms that extract, produce, distribute or sell fossil fuels. Those suits generally seek to hold companies accountable for alleged contributions to climate change and related costs.
The scientific premise cited in these complaints is that the combustion of fossil fuels releases greenhouse gases such as carbon dioxide into the atmosphere, which increases the trapping of the sun’s heat and over time raises average global temperatures. The Boulder litigation frames municipal costs as a downstream consequence of rising temperatures and associated climate effects.
The Supreme Court has addressed similar procedural issues in the past. It previously declined to grant a bid from Sunoco and other oil companies to dismiss a climate-related lawsuit filed by Honolulu after Hawaii’s highest court permitted that case to proceed. The Honolulu action alleges the companies bear responsibility for contributing to extreme weather and a notable rise in sea level along the Honolulu Pacific coastline, developments that plaintiffs link to flooding, erosion and beach loss.
Case status: U.S. Supreme Court will review ExxonMobil and Suncor Energy's appeal after the Colorado Supreme Court denied a request to dismiss in May 2025. The underlying Boulder suit remains active, seeking unspecified monetary damages tied to climate mitigation costs.