The U.S. Supreme Court declined Wednesday to block Boulder, Colorado's climate-deception lawsuit against ExxonMobil and Suncor Energy, allowing the case to return to state court for trial.

Boulder, joined by Boulder County and San Miguel County, sued the two oil companies in 2018, alleging they concealed known climate risks of fossil fuels and seeking damages for local infrastructure costs. The companies had argued the claims were governed by federal law and should be dismissed.

The outcome mirrors the court's earlier reluctance to intervene in similar disputes. In 2023, the justices declined to hear appeals from Suncor and others seeking to move comparable cases to federal court, leaving suits in Colorado, Hawaii and Rhode Island to proceed under state consumer-protection and nuisance laws.

Shares of ExxonMobil and Suncor showed limited movement, as investors have largely priced in prolonged litigation. The American Petroleum Institute criticised the ruling, arguing that climate policy belongs with Congress and regulators, not state courtrooms.

Environmental lawyers called the decision a milestone for accountability. "This clears the way for Boulder to make its case before a jury," said a spokesperson for the Colorado city's legal team. "Communities should not bear the full cost of a harm the defendants understood decades ago."