California Attorney General Rob Bonta on Friday, October 2, led a coalition of 26 states, counties and cities in suing the National Highway Traffic Safety Administration (NHTSA) over its newly finalized corporate average fuel economy (CAFE) standards for new passenger cars and light trucks. Filed in the U.S. Court of Appeals for the First Circuit, the lawsuit alleges the rule is contrary to law and that NHTSA violated its congressional mandate to set fuel-economy standards at their "maximum feasible" level. The plaintiffs include New York, New Jersey, Washington, Colorado, Massachusetts, Michigan, Arizona and Connecticut, plus New York City, Chicago, Denver and the District of Columbia. Environmental and consumer groups filed a separate parallel lawsuit.
The fight is about numbers. The Biden-era target for model-year 2031 was a fleet average of 50.4 miles per gallon; NHTSA's rule finalized this week cuts it to 34.9 mpg — roughly a 30 percent reduction. Bonta argues the new targets require less efficiency than what the U.S. vehicle fleet actually achieved in 2021, effectively reversing decades of progress.
The plaintiffs seized on a technical maneuver. NHTSA sets standards by modeling the current fleet, then estimating how much more efficient automakers could get. In past rulemakings — including during the first Trump administration — the baseline fleet included the millions of electric vehicles already on American roads. This time the Transportation Department simply dropped EVs from the baseline. A lower starting point makes a lower "maximum feasible" ceiling easier to justify, and makes weaker standards for gasoline vehicles look reasonable. Bonta called the analysis "flawed" and "dramatically distorted."
The lawsuit landed as California's average gasoline price hit $6.40 a gallon, up nearly $2 from a year ago — driven by global oil supply disruptions tied to the U.S.-Israeli war with Iran that began in February. The plaintiffs' logic: weakening efficiency standards during an energy crunch directly contradicts the Energy Policy and Conservation Act's core mandate to conserve energy and protect national security through reduced oil dependence. The law was established in 1975 after the Arab oil embargo, and the "maximum feasible" standard has been on the books ever since.
Bonta's statement pulled no punches: "The President started a war that has created volatility in oil markets, disrupted global energy supplies, and left families and businesses paying the price at the pump. Yet, the Trump Administration is attempting to gut fuel economy standards and force Americans to spend billions more on gas while poisoning the air in our communities. Let's be clear: The Trump Administration is doing this to line the pockets of their Big Oil donors."
New Mexico Attorney General Raúl Torrez joined the announcement: "Working families should not have to pay more at the pump because the federal government has chosen to weaken commonsense fuel-efficiency standards."
The Transportation Department tells the opposite story: the change could save American taxpayers $138 billion over the next five years, and new vehicles will cost less. The price, which the department's own estimates concede, is higher fuel consumption and carbon dioxide emissions for decades. Environmental groups say bluntly that 2031-model vehicles will be less efficient than the current fleet.
This was not the week's only climate case. On October 1, New York Attorney General Letitia James led a coalition of 25 states and cities in suing the Environmental Protection Agency to block its repeal of the 2024 Carbon Pollution Standards, which required U.S. power plants to cut greenhouse gas emissions by installing carbon capture technology. That suit was filed in the U.S. Court of Appeals for the D.C. Circuit. Power plants are the second-biggest source of U.S. greenhouse gas emissions after vehicles, accounting for one-quarter of American carbon dioxide emissions. "Dismantling these protections is a betrayal of American families," James said.
The two lawsuits point to the same battlefield: the Trump administration is systematically dismantling Biden-era climate and efficiency regulation, and Democratic state attorneys general are choosing to fight it out in court, rule by rule.