California and 20 States Sue to Block Fuel Standard Rollback

California and nearly two dozen other states and cities filed a lawsuit in the U.S. Court of Appeals for the First Circuit on Friday to block the Trump administration from weakening fuel efficiency standards for new cars and light trucks. The legal challenge targets a U.S. Department of Transportation rule that lowers the required average fuel efficiency for model year 2031 to 34.9 miles per gallon, a significant decrease from the 50.4 miles per gallon established by the Biden administration.

Rob Bonta, the Attorney General of California, argued that the rollback is illegal because it ignores electric vehicle technology and fails to set standards at the maximum feasible level. Bonta claimed the administration manipulated its analysis to reach a desired result.

Transportation Secretary Sean Duffy defended the rules, characterizing the previous standards as an illegal electric vehicle mandate that inflated car prices. While the Trump administration estimates the new rules will reduce car prices by an average of $1,289, the analysis indicates drivers will pay $1,624 more in fuel costs over time.