The US Environmental Protection Agency (EPA) has issued a final decision disapproving of California’s Heavy‑Duty Inspection and Maintenance Regulation as it applies to vehicles registered outside the state or outside the country.
The ruling, announced January 27, 2026, concludes that California’s plan to include out‑of‑state and out‑of‑country heavy‑duty trucks in its State Implementation Plan does not meet federal requirements under Section 110 of the Clean Air Act.
According to the agency, California did not provide the necessary assurances that applying the rule to non‑California vehicles would comply with the US Constitution’s Commerce Clause, which restricts states from interfering with interstate and international trade. EPA officials also stated that extending the rule to foreign‑registered vehicles would conflict with federal authority over foreign policy matters.
EPA Administrator Lee Zeldin said, “The Trump EPA will never back down from holding California accountable and stopping them from imposing unnecessary regulations on the entire nation. If California had its way, prices would skyrocket for truckers and businesses across America. Affordable trucks are vital for keeping food and goods moving and prices low for families.”
While the agency rejected the provisions affecting out‑of‑state and out‑of‑country vehicles, it approved the portion of the regulation that applies to non‑gasoline heavy‑duty vehicles over 14,000 pounds registered in California. That portion will become federally enforceable under the State Implementation Plan.
The EPA noted that the decision followed a 30‑day public comment period before finalization. The agency said it remains committed to implementing the Clean Air Act as written, while ensuring that state‑level regulations do not extend beyond their legal scope.