The Colorado Air Quality Control Commission partially adopted California’s rules in 2023, which was allowed under the Environmental Protection Agency’s regulations.

California leaders said the state intends to challenge the move in court, and to find new ways to move drivers toward electric vehicles.

Trump also signed measures to overturn state policies curbing tailpipe emissions in certain vehicles and smog-forming nitrogen oxide pollution from trucks. Trump called California’s regulations “crazy” at a White House ceremony where he signed the resolutions.