The EPA is taking aim at California’s “Clean Truck Check” smog rules, saying that forcing out-of-state trucks to comply could break federal law.

What’s going on: On August 25, 2025, the EPA said it plans to shoot down the part of California’s program that requires out-of-state and foreign trucks to follow their heavy-duty inspection and maintenance (HD I/M) rules.

• California’s Clean Truck Check has been in place since 2023 and targets diesel trucks over 14,000 pounds running in the state.
• The program requires emissions testing with on-board diagnostics, roadside checks, and regular compliance reporting for all trucks—including those just passing through.
• CARB claims the rule helps cut smog and could prevent over 7,500 early deaths by 2037, according to the California Air Resources Board.

Why it matters: The EPA argues that California is overstepping by regulating trucks from other states, which could hurt interstate commerce and raise costs for truckers.

• The Commerce Clause of the U.S. Constitution gives the federal government—not states—the power to regulate interstate trade.
• EPA Chief Lee Zeldin said, “California was not, and has never been, duly elected by the American people to run our great country.”

The EPA is taking public comments before making a final call on California’s rule for out-of-state trucks.