California’s push for its controversial “clean truck” regulations has just taken a devastating blow. A federal court has frozen the Clean Truck Agreement, dismantling the state’s last attempt to enforce environmental standards that Congress—and President Donald Trump—had already struck down.

The conflict began when California insisted on enforcing the Advanced Clean Trucks rule and other zero-emission regulations, even after Congress repealed them through the Congressional Review Act. Despite this, Governor Gavin Newsom signed an executive order directing the state to move forward and even reward manufacturers that complied with standards already invalidated.

Tensions erupted when major manufacturers—Daimler, Volvo, Paccar, and International—who had signed the “Clean Truck Alliance” in 2023, were pressured by the Department of Justice to abandon the agreement, which the agency considered illegal. Shortly after, the FTC closed an antitrust investigation because the manufacturers agreed not to enforce the pact.

But California didn’t stop. CARB warned manufacturers that the rules could be applied retroactively if the state prevailed in court. Then it sued the companies for breach of contract.

Everything collapsed on October 31. Judge Dena Coggins granted the freeze, stating that California’s arguments had “evaporated” and now “ring hollow.”

With the agreement halted and no federal backing, California faces its biggest defeat yet in its battle to impose strict emissions rules. The state is left with only one option: to try to overturn Congress’s resolutions in court—a steep uphill fight.