A group of semis at a truck stop in rural California.
SACRAMENTO - Saying the state essentially forced her hand, a federal judge has blocked the state of California from attempting to enforce their new so-called "Clean Truck" emissions standards while a lawsuit plays out over whether the state ever actually had the authority to attempt to force truck makers to redesign their engines in a potentially impossible attempt to comply with the state's emissions goals.
On Oct. 31, U.S. District Judge Dena Coggins in California's Eastern District federal court granted a preliminary injunction against the California Air Resources Board (CARB) and its so-called "Clean Truck Partnership" agreement.
In her ruling, Coggins appeared to spend much of the decision mostly explaining why the injunction requested by attorneys for the state had repeatedly asserted CARB and the California state government under Gov. Gavin Newsom had no intent to attempt to enforce the regulations that were the subject of the litigation.
However, Coggins said CARB itself demonstrated the possibly misleading nature of those assertions, when it filed a legal action in California state court seeking to obtain an order forcing truck makers to comply with the regulations, even as the truck makers asked the federal court to determine if the regulations were ever lawful.
"At the time Defendants raised these arguments..., there may have been some persuasive weight to them," Coggins wrote.
"But whatever weight those arguments may have carried has since evaporated, and Defendants’ arguments now ring hollow: On October 27, 2025, just days before the scheduled hearing on Plaintiffs’ motion for a preliminary injunction, CARB filed a breach-of-contract lawsuit against the OEM (truck maker) Plaintiffs seeking specific performance of the Clean Truck Partnership, i.e., seeking a court order requiring (truck makers) to certify to CARB’s standards—regardless of whether those standards were ever the subject of a preemption waiver" from the U.S. Environmental Protection Agency, as required by law, Coggins wrote.
As a result, Coggins said a preliminary injunction is now required to prevent California from attempting to force truck makers to comply with regulations that remain in legal doubt, and which California had already told the court they would not seek to enforce for at least a decade in the future.
The injunction also would block CARB from continuing with its state court lawsuit against truck makers.
The court fight began earlier this year when truck makers sued the state of California, seeking a court order declaring CARB had exceeded its authority by implementing so-called "Clean Truck" emissions standards.
Specifically, the emissions standards would severely tighten rules governing allowed nitrogen oxide (NOx) emissions from the engines of semi trucks and other large commercial vehicles, essentially taking the allowable emissions to zero.
Known as the Advanced Clean Trucks regulations, the rules build on and rely on the authority California claims it has under a special waiver from Congress through the federal Clean Air Act to more stringently regulate vehicle emissions than would otherwise be allowed under federal law.
California has held the so-called waiver for decades. However, in recent years, California has ignited controversy, as Democrats have sought to use the waiver to impose ever tighter emissions regulations, with supporters declaring publicly their goal was to use the regulations to impose emissions rules so strict they could eventually prohibit internal combustion engines altogether.
President Donald Trump and other states have protested California's actions, declaring California has abused its special waiver and its outsized market power, as the country's largest state economy, to attempt to dictate vehicle emissions standards for the entire U.S.
With that in mind, Republicans in Congress moved to revoke California's waiver through legislation earlier this year.
California has sued over that decision, saying Congress lacked the authority to revoke the waiver in the manner it did and California essentially has a legal right to set emissions standards as it sees fit.
In earlier years, however, the trucking industry was among those pushing back on the tightening regulations, warning CARB and California Democrats that the regulations were likely being illegally imposed and were all but impossible for the industry to achieve in the timeline demanded by CARB and California Democrats.
The state then entered into a so-called "Clean Truck Partnership" agreement with some of the large truck makers, under which the truck makers, or "original equipment manufacturers" (OEM), agreed to comply with some of the regulations sought by CARB.
However, after Congress moved to revoke California's emissions regulating waiver, the trucking industry and Trump White House filed suit, asserting California was attempting to implement regulations on the trucking industry that it lacked the legal authority to impose.
Specifically, the industry and Trump administration argue California's "Advanced Clean Truck" standards and other emissions rules are preempted by federal law.
California has disputed those contentions in court. And the state has also repeatedly claimed the truck makers were never under any kind of threat at this time, as the state did not intend to enforce the regulations any time soon.
However, as Judge Coggins noted in her ruling, the state then moved separately in state court to attempt to enforce the Clean Truck Partnership agreement, seeking a court order declaring the truck makers had breached the deal by refusing to comply with the emissions regulations specified in the Partnership agreement while their challenge played out in federal court.
In a statement following the ruling published in other reports, truck maker Daimler Trucks North America said they welcomed the judge's "prompt decision" blocking California from attempting to enforce challenged rules, even as the industry seeks clarity on the legality of the rules the state wishes to enforce.
