The US Department of Justice (DOJ) and Department of Transportation (DOT) on Thursday filed a lawsuit against the California Air Resources Board (CARB) in an effort to block the state from enforcing carbon dioxide (CO2) and zero-emission vehicle (ZEV) mandates on the grounds that federal law prohibits state regulation in this area.

The federal lawsuit targets two CARB regulations. First, the fleetwide CO2 emission standards, codified under California Code of Regulations Title 13, Sections 1961.3 and 1961.3.1, which requires automakers selling vehicles in California to meet increasingly stringent fleet-wide carbon emission targets, currently capped at 131 grams per mile for passenger cars in model year 2025 and beyond. Second, the ZEV sales mandate, codified under Sections 1962.2 and 1962.2.1, which requires that a set percentage of each manufacturer’s California sales be zero-emission vehicles, a figure that sat at 22 percent for 2025 and was designed to climb to 100 percent by 2035. The ZEV sales mandate was invalidated in June 2025 via the Congressional Review Act. CARB is currently enforcing both regulations under an emergency mandate.

The DOJ and DOT argue that both regulations are preempted by the Energy Policy and Conservation Act of 1975 (EPCA), which gives the federal government exclusive authority over vehicle fuel economy standards and bars states from adopting any regulation “related to” fuel economy. Thursday’s complaint argues that California’s regulations are inherently tied to the fuel economy and thus barred by the EPCA. Further, the government argues that the Clean Air Act waivers, which California has long relied on to defend its emissions rules, are irrelevant, as those waivers only exempt California from the Clean Air Act‘s preemption provisions, and the EPCA is an entirely separate statute with its own preemption clause and no waiver mechanism.

In a statement, Attorney General Pam Bondi explained Thursday’s lawsuit and offered additional support for President Donald Trump’s “Freedom Means Affordable Cars” initiative:

Oppressive, expensive electric vehicle mandates drive up costs for American consumers and violate federal law…California is using unlawful policies from the last administration to create exorbitant costs for our citizens — this Department of Justice is proud to stand with President Trump and Secretary Duffy to bring litigation that will make life more affordable for American consumers.

The DOJ and DOT ask for declaratory judgments on both regulations and permanent injunctions barring CARB from enforcing or adopting either regulation. The complaint further calls out CARB’s in-development Advanced Clean Cars III regulations and asks the court to intervene before any enforceable regulations emerge.

Thursday’s complaint represents the latest challenge to California’s green energy initiatives, following suits filed by truck manufacturers and fuel industry groups.