Justice Department Sues California to Halt Enforcement of Preempted Truck Emissions Standards

(Advanced Clean Tech News) The U.S. Department of Justice (DOJ) filed two federal court complaints last week against the California Air Resources Board (CARB), challenging the enforcement of emissions standards that DOJ contends are preempted under the Clean Air Act.

According to the DOJ, CARB is enforcing these standards through its Clean Truck Partnership, despite recent congressional actions invalidating EPA’s previously granted preemption waivers. In June 2025, President Trump signed joint congressional resolutions that nullified EPA waivers for CARB’s heavy-duty truck regulations. DOJ argues that, without those waivers, enforcement of these regulations violates federal law.

Acting Assistant Attorney General Adam Gustafson of the Environment and Natural Resources Division said the state’s actions are an attempt to bypass federal authority, stating that “agreement, contract, partnership, mandate — whatever California wants to call it, this unlawful action attempts to undermine federal law.”

The DOJ’s Environment and Natural Resources Division (ENRD) filed motions to intervene as plaintiffs in related cases pending in the Eastern District of California and the Northern District of Illinois. In parallel, the DOJ filed appellate motions in a separate proceeding concerning light-duty vehicle emissions rules, which it also alleges are preempted.

As stated in the press release, these actions advance “President Donald J. Trump’s commitment to end the electric vehicle (EV) mandate, level the regulatory playing field, and promote consumer choice in motor vehicles.” READ MORE

Excerpt from U.S. Department of Justice: The Justice Department this week filed two complaints in federal courts against the California Air Resources Board (CARB) regarding the State’s enforcement of preempted emissions standards through its so-called “Clean Truck Partnership” with heavy-duty truck and engine manufacturers. A parallel filing in the court of appeals addresses CARB’s rules for light-duty vehicles, which are also preempted. These actions advance President Donald J. Trump’s commitment to end the electric vehicle (EV) mandate, level the regulatory playing field, and promote consumer choice in motor vehicles.

The Clean Air Act preempts state regulation of vehicle emissions unless the Environmental Protection Agency (EPA) grants California a preemption waiver. Under the Biden administration, EPA granted preemption waivers for two CARB regulations imposing stringent emissions standards for heavy-duty trucks. The goal of CARB’s regulations is to implement an EV mandate in California and in other states that adopt California’s rules.

In June 2025, President Trump signed into law congressional resolutions under the Congressional Review Act, invalidating EPA’s preemption waivers for CARB’s heavy-duty truck regulations. Without these waivers, the Clean Air Act prohibits CARB from attempting to enforce those regulations. Yet, in an affront to the rule of law, CARB seeks to circumvent that prohibition by enforcing the preempted emissions standards through the Clean Truck Partnership. The Justice Department’s Environment and Natural Resources Division (ENRD) filed the complaints with motions to intervene in pending cases in the Eastern District of California and Northern District of Illinois.

“Agreement, contract, partnership, mandate — whatever California wants to call it, this unlawful action attempts to undermine federal law,” said Acting Assistant Attorney General Adam Gustafson of ENRD. “President Donald Trump and Congress have invalidated the Clean Air Act waivers that were the basis for California’s actions. CARB must respect the democratic process and stop enforcing unlawful standards.”

In related actions, ENRD moved to dismiss as moot two sets of cases in the U.S. Court of Appeals for the Ninth Circuit where industry groups had challenged EPA’s preemption waivers for cars. Those cases are now moot because Congress’s joint resolutions nullified the controversial preemption waivers.

ENRD is responsible for bringing cases against those who violate the nation’s environmental laws, as well as defending the federal government in litigation arising under a broad range of environmental statutes. The division is the nation’s environmental lawyer, and the largest environmental law firm in the country.

Chief of Staff and Senior General Counsel John Adams and Deputy Assistant Attorney General Robert Stander of ENRD filed the complaints, and attorneys with ENRD’s Appellate section are handling the cases in the Ninth Circuit. The EPA is a co-plaintiff in the filings. The U.S. Attorney’s Offices for the Northern District of Illinois and the Eastern District of California also provided assistance.