The U.S. government has filed a lawsuit against California regulators in a major legal challenge to the state’s electric vehicle policies, arguing that federal law prohibits states from imposing regulations that effectively dictate national fuel economy standards.
The complaint, filed by the U.S. Department of Justice and the Department of Transportation, targets two rules issued by the California Air Resources Board (CARB). Federal officials say the regulations conflict with federal authority over vehicle fuel economy established under the Energy Policy and Conservation Act of 1975.
Regulations at Issue
The lawsuit challenges two CARB rules governing vehicle emissions and sales in California.
The first involves fleetwide carbon dioxide emission standards codified in the California Code of Regulations. These rules require automakers selling vehicles in the state to meet strict carbon emissions limits, currently set at 131 grams of CO₂ per mile for passenger vehicles beginning with the 2025 model year.
The second rule is California’s zero-emission vehicle (ZEV) sales mandate, which requires automakers to ensure that a portion of their vehicles sold in the state are electric or otherwise produce zero emissions. The requirement reached 22 percent for the 2025 model year and was scheduled to rise steadily until all new vehicles sold in the state are zero-emission by 2035.
Although Congress invalidated the ZEV sales mandate in June 2025 through the Congressional Review Act, federal officials say California regulators are continuing to enforce the standards through emergency measures.
Federal Government’s Legal Argument
In the complaint, federal attorneys argue that California’s regulations are preempted by the Energy Policy and Conservation Act because they are directly tied to fuel economy standards, an area Congress reserved for federal regulation.
The lawsuit asserts that EPCA prohibits states from adopting rules “related to” fuel economy, and the federal government contends California’s emissions limits and electric vehicle mandates inevitably influence vehicle fuel efficiency.
Federal officials also dispute California’s longstanding reliance on waivers under the Clean Air Act, which historically allowed the state to adopt stricter emissions rules than federal standards.
According to the complaint, those waivers apply only to the Clean Air Act’s preemption provisions and do not override EPCA’s separate restrictions on state fuel economy regulation.
Administration’s Position
In a statement accompanying the lawsuit, U.S. Attorney General Pam Bondi said the policies place an unnecessary burden on consumers.
“Oppressive, expensive electric vehicle mandates drive up costs for American consumers and violate federal law,” Bondi said. “California is using unlawful policies from the last administration to create exorbitant costs for our citizens.”
Bondi said the Justice Department is acting in support of President Donald Trump and Transportation Secretary Sean Duffy as part of the administration’s “Freedom Means Affordable Cars” initiative.
Broader Legal Fight
The federal lawsuit asks a court to issue declaratory judgments declaring the California regulations unlawful and to permanently block CARB from enforcing them.
It also seeks preemptive judicial intervention against CARB’s proposed Advanced Clean Cars III program, which could impose additional vehicle emission requirements in the future.
The case represents the latest chapter in an ongoing legal battle over California’s aggressive climate policies. The state has long set stricter emissions standards than federal regulators, influencing national vehicle design because automakers often align their fleets with California’s rules.
Industry groups, including truck manufacturers and fuel industry organizations, have already filed separate lawsuits challenging California’s regulations, arguing they effectively create a nationwide electric vehicle mandate.
Legal analysts say the case could become a significant test of federal preemption doctrine and the balance of power between state environmental authority and federal energy law.
What Comes Next
If the federal government prevails, the ruling could sharply limit California’s ability to regulate vehicle emissions through policies that indirectly affect fuel economy.
If California wins, it could reinforce the state’s role as a leader in setting environmental standards that shape the national auto market.
The case is expected to move through federal courts in the coming months.
