California: Clean Truck Check Rules Still in Force for Out-of-State Trucks, Despite EPA Disapproval

February 05, 2026

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by Deborah Lockridge (Heavy Duty Trucking) The Environmental Protection Agency said California can’t enforce its Heavy-Duty Inspection and Maintenance Regulation, known as Clean Truck Check, on vehicles registered outside the state. But California said it will keep enforcing the rule.

The Environmental Protection Agency said California can’t enforce its Heavy-Duty Inspection and Maintenance Regulation, known as Clean Truck Check, on vehicles registered outside the state. But California said it will keep enforcing the rule.

The state implemented the rule as part of its efforts to meet air quality standards by ensuring heavy-duty vehicle emissions control systems operate properly throughout the life of the vehicle and necessary repairs are made in a timely manner. Clean Truck Check requires reporting, payment of annual compliance fees, and vehicle emissions testing.

In a news release, EPA said that California’s attempt to establish the program in its State Implementation Plan for heavy-duty vehicles that pass through California, regardless of where the vehicle was registered, may be in conflict with the U.S. Constitution’s Commerce Clause.

However, according to published reports, the California Air Resources Board said it will continue to apply the program to all trucks, including those registered out of state.

Why Did EPA Deny California’s Smoke Check?

EPA determined that California failed to provide necessary assurances, as required by Section 110 of the Clean Air Act, that implementing the Regulation would be consistent with the U.S. Constitution’s Commerce Clause, which prevents states from interfering with interstate and international trade.

The agency said it has approved the regulation only as it applies to in-state-registered vehicles.

The Safe Bet: Continue to Follow Clean Truck Check Rule

“This announcement is a whole lot of bluster about bean counting,” said CARB spokesperson Lindsay Buckley in a statement widely reported by the media.

“EPA has no authority over this program, and we will continue to enforce the law to ensure that all trucks coming into and operating in California abide by the same rules — even if EPA doesn’t want to give us credit.”

As Politico explained, in practice, the rule remains in effect for out-of-state trucks, according to CARB spokesperson Buckley.

“EPA’s disapproval means that the air quality improvements stemming from those inspections will not count toward the list of emissions reductions efforts California has employed to clean up its air under the Clean Air Act, which could require CARB to take additional emissions reduction steps.” READ MORE

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Excerpt from California Energy Journal: The U.S. Environmental Protection Agency (EPA) issued a final rule January 27, 2026 disapproving of California’s inspection and maintenance requirements on out-of-state trucks passing through the state. The EPA approved California’s Heavy-Duty (HD) Inspection and Maintenance (I/M) Regulation only as it applies to in-state registered vehicles. The EPA proposed its disapproval of the so-called Clean Truck Check rule on out-of-state vehicles in August 2025.

The EPA ruled that an inspection and maintenance program in the State Implementation Plan (SIP) for heavy-duty vehicles that pass through California may violate the Constitution’s Commerce Clause. The EPA stated in its ruling that “extending the regulation to out-of-state vehicles serves the illegitimate objective of outsourcing the costs of attaining the [National Ambient Air Quality Standards] within California to other States and vehicle owners and operators in those States, rather than identifying additional emissions reduction strategies within the traditional ambit of purely in-state sources encompassed within and creditable to the State of California.” The EPA also noted that extending the requirement to vehicles registered in Mexico and Canada could intrude on federal authority over foreign relations and interstate commerce.

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The California Air Resources Board (CARB) indicated that it will continue enforcing the Clean Truck Check against all vehicles that operate in the state, even if the emissions reductions from out-of-state trucks cannot be credited under the state’s SIP. A CARB official responded that the EPA “has no authority over this program and we will continue to enforce the law to ensure that all trucks operating in California abide by the same rules — even if EPA doesn’t want to give us credit.”

The EPA establishes national ambient air quality standards (NAAQS) under the Clean Air Act for certain air pollutants. States must submit SIPs for the implementation, maintenance, and enforcement of the NAAQS within each state. These plans include emissions limitations and other controls.

California officials have argued that out-of-state and foreign-registered trucks contribute a significant share of NOx and particulate emissions in California and should be subject to the same inspection and compliance requirements as in-state vehicles. In 2023, the California Air Resources Board (CARB) adopted the Heavy-Duty Inspection and Maintenance (I/M) rule to reduce emissions of particulate matter and nitrogen oxide. The rule mandates roadside emissions screening and periodic emissions testing for non-gasoline heavy-duty vehicles operating in California.

The EPA’s decision to reject the out-of-state portion of the rule is a significant federal intervention in the SIP and underscores ongoing tensions between California’s climate policy and the Trump EPA’s regulatory priorities.

Since taking office, the Trump administration has revoked California’s vehicle emissions waivers, which included stringent emissions requirements for heavy-duty vehicles. It has also challenged the state’s Clean Truck Partnership, which aims to advance zero-emission vehicles (ZEVs) for the commercial trucking industry. READ MORE

Excerpt from Politico: Details: CARB pushed back last year on EPA’s proposal, noting that the agency alleged in its press release announcing the proposed decision that California’s rule was “based on an extreme climate ideology.”

“EPA’s gratuitous and prejudicial statements … are utterly inconsistent with the requirements of reasoned decision-making and simply arbitrary and capricious,” CARB wrote in September comments.

In Tuesday’s final decision, EPA rejected CARB’s allegation that its motivation was pretextual.

“Commenters are taking the press release out of context to avoid grappling with the rationale and basis for decision included in the proposed rule,” the agency wrote.

The state also argued it had addressed the constitutional issues with inspecting out-of-state vehicles that were laid out by EPA.

But in its final decision, EPA maintained that the out-of-state inspections burdened parties outside the state with the costs of emissions reductions to achieve local air quality gains, running afoul of both the Constitution and the Clean Air Act.

“Put another way, extending the regulation to out-of-state vehicles serves the illegitimate objective of outsourcing the costs of attaining the [National Ambient Air Quality Standards] within California to other States and vehicle owners and operators in those States, rather than identifying additional emissions reduction strategies within the traditional ambit of purely in-state sources encompassed within and creditable to the State of California,” EPA wrote.

Practically speaking, the rule remains in effect for out-of-state trucks, according to CARB spokesperson Buckley. EPA’s disapproval means that the air quality improvements stemming from those inspections will not count toward the list of emissions reductions efforts California has employed to clean up its air under the Clean Air Act, which could require CARB to take additional emissions reduction steps.

What’s next: The final rule was signed by acting EPA Region 9 Administrator Michael Martucci and will be published in the Federal Register soon. READ MORE