Attorneys general from 21 states and the District of Columbia went to federal court on Oct. 2 to try to overturn the Trump administration’s rollback of fuel economy standards for new cars and light trucks. They say drivers would lose nearly $220 billion in fuel savings under the weaker rules. The suit was filed in the U.S. Court of Appeals for the First Circuit and challenges a final rule from the National Highway Traffic Safety Administration.

The 21 states and four cities

California Attorney General Rob Bonta’s office lists the plaintiffs in its announcement of the lawsuit. The 21 states are Arizona, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New Mexico, New York, North Carolina, Oregon, Rhode Island, Vermont, Washington and Wisconsin. The District of Columbia joined them, and so did four cities: Chicago, Denver, New York City and San Francisco. Connecticut’s attorney general describes the group as a coalition of 26 states, counties and cities.

What the rule changes

Federal fuel economy standards, known as CAFE, set an average mileage that each automaker’s new cars and light trucks must reach. According to New York Attorney General James’s office, NHTSA’s final rule sets a fleet average of 34.9 miles per gallon by 2031, where the earlier goal was over 50. The states say the standards for the next five years ask for less efficiency than the U.S. fleet actually achieved in 2021.

People who plan to buy a car in the next few years are the ones this touches most directly. Lower mileage targets can mean new models that burn more fuel than they otherwise would. The states put a number on that cost for the country as a whole, and they have not published one for a single driver.

The 34.9 mpg fleet average for 2031 is the number the states want the First Circuit to throw out.

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Where the $220 billion comes from

The figure is the coalition’s own estimate of fuel savings that drivers would have had under the previous standards. Bonta’s office says NHTSA “tries to paper over nearly $220 billion in lost fuel savings.” It is a national total added up across all drivers and years, not an amount any one household should expect to lose. None of the state releases break it down per driver or per car.

The states’ releases do not include a response from NHTSA.

The legal claims

The states argue the rule is contrary to law, falls short of the “maximum feasible” standard that federal law sets for fuel economy, and is arbitrary and capricious. Their suit says the rule violates the Administrative Procedure Act and the Energy Policy and Conservation Act. Minnesota Attorney General Keith Ellison’s office adds that the rule ends the CAFE credit trading program in 2028, and that the states argue NHTSA’s reasoning ignores the millions of electric vehicles already on the road.

Bonta said in the release, “Let’s be clear: The Trump Administration is doing this to line the pockets of their Big Oil donors.” That is the California attorney general’s accusation, and the administration has not been quoted answering it in the releases. Connecticut Attorney General Tong pointed to pump prices, saying, “Gas is pushing five dollars a gallon right now.” Michigan Attorney General Dana Nessel’s office posted its release on Oct. 5, three days after the filing. Nessel said, “Michigan knows better than most what is at stake when it comes to fuel economy and the future of the auto industry.”

The filing starts the case and decides nothing yet. The state releases give no schedule for written arguments or a ruling.

What car shoppers can watch

The agency behind the rule is NHTSA, and its site, nhtsa.gov, is the free place to follow federal fuel economy rulemaking. The case itself sits in the First Circuit, and the attorneys general’s releases are the quickest public summary of what the states are asking the court to do.

For anyone shopping for a car now, the mileage rating on each window sticker is the number that sets what a vehicle will cost to fuel. Comparing the combined miles per gallon of two similar models, then multiplying the difference by the miles driven in a year, shows the gap in plain dollars.

What the court does with the 34.9 mpg target is the open question. The state releases list the First Circuit as the court and Oct. 2 as the filing date, and they say nothing about a hearing yet.

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This article was produced with AI assistance and edited for accuracy against the sources linked above.