EPA says California’s smog checks for out-of-state semi trucks may be unconstitutional

The U.S. Environmental Protection Agency (EPA) announced plans to take action against California’s “Clean Truck Checks” for out-of-state trucks, claiming that the program could violate the U.S. Constitution’s Commerce Clause and the Clean Air Act.

EPA Head: California’s Vehicle Emission Policies Increase Cost Of Living

On Monday, August 25, 2025, the EPA announced a proposal “to disapprove of California’s Heavy-Duty (HD) Inspection and Maintenance (I/M) Requirements as it applies to out-of-state and out-of-country vehicles.”

“California was not, and has never been, duly elected by the American people to run our great country,” said EPA Administrator Lee Zeldin. “The state’s power grab knows no bounds. EPA will not allow California to violate federal law, and we will not sit idly by while, in the name of climate change, they raise the cost of living on all Americans who rely on truck drivers and the products they deliver across the country.”

California’s Clean Truck Checks Under Fire From Feds

The HD I/M Program, also known as “Clean Truck Checks” or “smog checks,” is a heavy-duty vehicle enforcement program in place since 2023 that is conducted by the California Air Resources Board (CARB) as part of Clean Air Act enforcement.

The Clean Truck Checks program focuses on non-gasoline combustion vehicles over 14,000 pounds operating in California, and it involves roadside emissions monitoring, emissions testing procedures using on-board diagnostics data, emissions checks and data reporting at required intervals, and compliance verification requirements for freight contractors, seaports, and rail yards.

The EPA has called into question whether California has the authority to enforce the HD I/M Program for out-of-state heavy duty trucks.

“EPA is proposing to deny these actions due to concerns that this requirement violates the U.S. Constitution’s Commerce Clause and this inconsistency with Federal law also violates Section 110 of the Clean Air Act,” the agency said.

The agency argues that the burden of the Clean Truck Checks is too great on interstate commerce, and that complying with the program adds significant cost for truckers operating in California. “Here, the Commerce Clause appears to prohibit the implementation of the HD I/M Regulation because its extraterritorial reach burdens interstate commerce … Burdens on interstate commerce are of particular concern when they impose costs on interstate trade,” the EPA said.

“Furthermore, by seeking to apply California’s HD I/M requirement to foreign vehicles, California’s State Implementation Plan (SIP) appears to ignore the fundamental principal that powers related to foreign affairs are solely vested by the Federal government. EPA will not allow California to violate federal law in a manner that foists yet another attack on truck drivers and engine manufacturers who provide the food and products we need to survive. California’s approach appears to be part of a larger strategy to drive out affordable trucks and products based on an extreme climate ideology,” the EPA continued.

The EPA will accept public comment on the proposal to disapprove part of the HD I/M requirements. You can view the EPA’s full notice to be published in the Federal Register on August 26 here.

Earlier this month, the U.S. Department of Justice filed suit in federal court against CARB regarding the State’s enforcement of preempted emissions standards through its so-called “Clean Truck Partnership” with heavy-duty truck and engine manufacturers.