United States sues California over ZEV, GHG emission rules

12 March 2026

The US Justice Department and Transportation Department have filed suit against the state of California, claiming that the California Air Resources Board (CARB) zero-emission vehicle (ZEV) and greenhouse gas (GHG) emissions ‌rules are illegal and preempted by federal law.

The lawsuit claims that California imposes an “illegal electric vehicle (EV) mandate” through what are effectively state-specific mileage requirements for car manufacturers, while federal law prohibits individual states from adopting regulations related to fuel economy.

The lawsuit seeks a ruling declaring that all ZEV mandates by California are ​unlawful and unenforceable. “This litigation will help automakers design and produce cars and trucks to ​meet one federal fuel economy regulation,” said Jonathan Morrison, the Administrator of the National Highway Traffic Safety Administration (NHTSA).

Last year, US Congress repealed an Environmental Protection Agency’s (EPA) waiver that permitted CARB to implement the Advanced Clean Cars II (ACC II) regulation. The ACC II package included the ZEV requirements for model year 2026 and later—which mandated that 100% of new light-duty vehicles sold in California from 2035 be ZEVs.

In February, the EPA repealed the 2009 Greenhouse Gas Endangerment Finding and all subsequent federal GHG emission standards for all vehicles and engines of model years 2012 to 2027 and beyond.

The lawsuit challenges California’s regulations as preempted under the Energy Policy and Conservation Act, which makes NHTSA the exclusive regulator of fuel economy in the United States. The litigation involves defendants California’s Air Resources Board and its executive officer in the United States District Court for the Eastern District of California.

Source: US DOT