Attorney General Phil Weiser joins lawsuit challenging federal fuel economy standards rollbacks

Attorney General Phil Weiser joins lawsuit challenging federal fuel economy standards rollbacks

Oct. 2, 2026 (DENVER) - Attorney General Phil Weiser today joined a coalition of 27 states, counties, and cities in filing a lawsuit against the National Highway Traffic Safety Administration challenging its final rule weakening corporate average fuel economy standards for new passenger cars and light trucks.

Historically, NHTSA's standards have reduced consumer costs by improving fuel efficiency for vehicles, placed downward pressure on gas prices by reducing fuel consumption, protected the U.S. economy from global oil shocks, and reduced pollution from tailpipes and refineries. However, the final rule significantly weakens fuel economy standards and hurts consumers and the environment. In the lawsuit filed today in the U.S. Court of Appeals for the First Circuit, the coalition alleges that the new rule is contrary to law and that NHTSA is violating its mandate from Congress to set fuel-economy standards at their "maximum feasible" level.

"The federal government's backsliding on standards for the next five years requires less fuel economy than what the U.S. fleet of new cars and trucks achieved in 2021. Rolling back fuel efficiency standards will cost Coloradans even more at the gas pump, harm public health, and undermine our nation's position in the EV market. These clean car rules are part of our clean energy future and that's why we are challenging this illegal action," said Attorney General Weiser.

In 1975, Congress enacted the Energy Policy and Conservation Act, which requires NHTSA to establish "maximum feasible" fuel economy standards for new vehicles that reflect technological feasibility, economic practicability, the effect of other motor vehicle standards of the government, and the need to conserve energy. In past rulemakings, including during the first Trump administration, NHTSA started from a baseline fleet that included the millions of electric vehicles that already existed on our nation's highways and roads and based fuel-economy standards on how additional technological improvements to gas-fueled cars could make that fleet more efficient. NHTSA never based fuel-economy standards on mandating automakers to produce more electric vehicles or requiring consumers to buy them.

The final rule ignores the presence of millions of electric vehicles in the nation's existing fleet, leading to a flawed, dramatically distorted analysis of the maximum feasible fuel economy level that the auto industry can achieve. NHTSA's novel reinterpretation of the law essentially renders the federal fuel-economy program toothless, unable to protect consumers against rising gas prices or ongoing global oil market shocks.

NHTSA has also utilized defective analyses of vehicle affordability and sales, fleet turnover, fuel savings, and vehicle safety to make a harmful and destructive rule look net-beneficial to society. For example, NHTSA tries to paper over nearly $220 billion in lost fuel savings - money that drivers would have saved at the pump under the previous fuel economy standards. It also refuses to consider hundreds of billions of dollars in future damages from climate change-driven disasters, disregarding the best science and research and effectively setting these costs at zero. Defying a longstanding and repeatedly affirmed congressional mandate, NHTSA claims that the U.S. does not need to conserve energy after all. Finally, NHTSA's rule will end the CAFE credit trading program in 2028, which will significantly harm electric vehicle industries that employ Americans and support the economy.

In today's lawsuit, the coalition alleges that NHTSA's final rule is arbitrary and capricious and violates the Administrative Procedure Act and the Energy Policy and Conservation Act.

In filing this lawsuit, Attorney General Weiser joins the attorneys general of California, Arizona, Connecticut, Delaware, Hawai'i, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, North Carolina, Oregon, Rhode Island, Vermont, Washington, Wisconsin, and the District of Columbia, as well as the City of Chicago, the City and County of Denver, the City of New York, and the City and County of San Francisco.

Read the petition for review (PDF).

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