DOJ sues CARB to block enforcement of ‘unlawful emissions standards for trucks’

The federal government has filed suit against the California Air Resources Board (CARB) over the state’s enforcement of truck emissions standards.

On August 15, 2025, the U.S. Department of Justice (DOJ) announced that two lawsuits were filed this week against CARB over California’s continued enforcement of preempted emissions standards through the “Clean Truck Partnership” with heavy-duty truck and engine manufacturers. 

“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 DOJ said.

Under the Biden Administration, the Environmental Protection Agency (EPA) granted California a Clean Air Act preemption waiver for two CARB regulations, allowing the state to impose stringent emissions standards for heavy-duty trucks. The DOJ says that CARB’s goal was to impose an EV mandate on California and other states that adopt California’s rules.

In June 2025, President Trump revoked the EPA-issued waivers.

“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 DOJ said.

The Clean Truck Partnership is an agreement between CARB, the Truck and Engine Manufacturers Association (EMA), and other major truck manufacturers to meet California’s vehicle standards and require the sale and adoption of zero-emission technology.

“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.”

Earlier this week, truck makers Daimler, Volvo, Paccar, and International Motors (formerly Navistar) also sued CARB over enforcement of Clean Truck Partnership standards.