DOJ sues California over truck emissions after Congress kills waivers

The Clean Air Act has given 🌴California the right to set its own vehicle emissions standards since 1967, when Congress wrote a special waiver provision in response to the state's severe smog crisis. Every state can either follow federal standards or opt into California's — under Section 177, 16 other states had adopted California's truck rules by 2025, making CARB's regulations a de facto national standard for roughly 40% of the U.S. vehicle market.

The Congressional Review Act of 1996 lets Congress overturn federal agency rules with a simple majority vote. No administration had ever used it to target a 🌴California vehicle waiver until Feb. 19, 2025, when Trump and EPA Administrator LZLee Zeldin formally asked Congress to review three CARB waivers. The Senate Parliamentarian ruled the CRA did not apply to waivers — but the Senate voted to override that ruling, setting a new precedent for congressional control over state environmental authority.

The House adopted three disapproval resolutions on April 30 and May 1 (H.J.Res. 87, 88, and 89). The Senate voted May 21-22. Trump signed all three on June 12, 2025, nullifying the EPA waivers for the Advanced Clean Trucks (ACT) rule, the Heavy-Duty Omnibus Low NOx regulation, and the Advanced Clean Cars II standard. After signing, Trump declared the 🌴California rules 'fully and expressly preempted by the Clean Air Act and cannot be implemented.'

CARB Chair LRLiane Randolph called the Senate vote 'unconstitutional, illegal and foolish' and said it was 'an assault on states' rights the federal administration claims to support.' Governor Gavin Newsom issued Executive Order N-27-25 on June 12, directing CARB to continue pursuing the objectives of the eliminated rules and develop alternative measures if court challenges to the disapprovals failed.

In July 2023, four major OEMs — Daimler Truck North America, Paccar, Volvo Group North America, and International Motors (parent companies of Freightliner, Western Star, Kenworth, Peterbilt, Volvo Trucks, Mack Trucks, and International) — signed the Clean Truck Partnership with CARB. Under the deal, CARB gave manufacturers more time and relaxed some NOx requirements. In exchange, manufacturers agreed to comply with CARB's zero-emission and criteria pollutant standards 'regardless of any attempts by other entities to challenge 🌴California's authority.'

The CRA resolutions put manufacturers in an impossible position. Federal law now said the CARB regulations were preempted and unenforceable. But the Clean Truck Partnership contract said the manufacturers had agreed to comply with those exact regulations regardless of their legal status. The DOJ called the Partnership an 'illegal' scheme and a 'stunning act of defiance' of federal law.

The DOJ sent cease-and-desist letters to Daimler Truck, Volvo, and International on Aug. 7, 2025, ordering them to stop complying with the Clean Truck Partnership. The DOJ said compliance with the Partnership constituted participation in an unlawful effort to enforce preempted 🌴California regulations. On Aug. 12, the FTC closed an antitrust investigation into the Clean Truck Partnership after the manufacturers agreed to ignore it.

On Aug. 15, the DOJ filed two lawsuits in federal court — one in the Eastern District of 🌴California and one in the Northern District of 🌽Illinois — seeking to bar CARB from enforcing its truck standards through the Partnership. Acting Assistant Attorney General AGAdam Gustafson said: 'Agreement, contract, partnership, mandate — whatever California wants to call it, this unlawful action attempts to undermine federal law.' A parallel filing in the Ninth Circuit addressed CARB's light-duty vehicle rules.

The four OEMs filed their own lawsuit against CARB on Aug. 11, describing themselves as 'caught in a crossfire between two sovereigns openly hostile to one another.' CARB's attorney general RBRob Bonta responded on Oct. 27 by filing a breach-of-contract lawsuit against the manufacturers, seeking to enforce the Clean Truck Partnership as a binding commercial agreement regardless of its regulatory status.

U.S. District Judge DCDena Coggins, a Biden appointee in the Eastern District of 🌴California, issued a preliminary injunction on Oct. 31 blocking the OEMs from having to comply with the Clean Truck Partnership. Coggins found that the manufacturers accounting for 99.9% of U.S. Class 8 retail sales in 2024 would suffer irreparable harm if denied relief. She also noted that CARB's breach-of-contract filing had undermined its own legal arguments: 'CARB's filing of that lawsuit is clearly an attempt to enforce pre-empted standards,' she wrote.

🌴California filed its own lawsuit challenging the constitutionality of the CRA resolutions, arguing Congress had no authority to use the CRA to strip a state waiver that Congress itself had authorized under the Clean Air Act. The 9th Circuit and the 🏛️D.C. Circuit are both potential venues for that challenge. Legal scholars are divided: some argue the CRA plainly allows Congress to disapprove any agency rule, including waiver grants; others argue the Clean Air Act created a specific statutory entitlement for California that cannot be revoked without amendment to the underlying law.

The House Energy & Commerce Committee also launched oversight inquiries into CARB's ongoing enforcement activities and communications with Section 177 states. Congressional investigators sought documents showing whether 🌴California was coordinating with other states to circumvent the preemption.

The real-world stakes are measured in air quality and public health. The 150 million Americans who live in areas that exceed federal air quality standards would have benefited from lower NOx and particulate matter emissions under the CARB truck rules. Heavy-duty diesel trucks are a primary source of NO2 and fine particulate matter (PM2.5) — pollutants linked to asthma, heart disease, and premature death — in communities near highways, ports, and distribution centers, which are disproportionately low-income communities of color.

Environmental justice advocates noted that the communities bearing the health costs of heavier pollution are rarely the same communities whose lawmakers voted to strip the 🌴California standards. The 17 Section 177 states that adopted California's rules did so precisely because their residents face the same air quality challenges as Californians — and they lost those standards too when Trump signed the CRA resolutions.

For the truck manufacturing industry, the CRA resolutions provided immediate regulatory relief from costly compliance timelines. The ACT rule required increasing percentages of zero-emission trucks in manufacturers' 🌴California fleets: 5% of Class 2b-3 trucks by model year 2024, rising to 75% by 2035. Cummins postponed the launch of its EPA-2027 X15 diesel engine to late 2026 on Aug. 6, citing regulatory uncertainty.

But the industry victory came with complications. Manufacturers who had made production and investment commitments under the Clean Truck Partnership — ordering parts, redesigning assembly lines — now faced stranded costs. And the lack of a unified national standard across the 17 Section 177 states created new uncertainty: manufacturers now have to produce different vehicle configurations for different regulatory environments, which can increase costs overall.