California is leading an 18-state coalition to sue the U.S. Environmental Protection Agency (EPA) to preserve a single vehicle emission standard for the United States.

The lawsuit, which was filed on 1 May in the United States Court of Appeals for the District of Columbia Circuit, seeks to set aside and hold unlawful the U.S. EPA’s effort to weaken the existing clean car rules. The lawsuit is based on the fact that the U.S. EPA acted arbitrarily and capriciously, failed to follow its own regulations and violated the Clean Air Act.

The 18 jurisdictions in the legal action represent approximately 43% of the U.S. automobile market and approximately 140 million people: California, Connecticut, Delaware, District of Columbia, Illinois, Iowa, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia and Washington.

“The states joining today’s lawsuit represent 140 million people who simply want cleaner and more efficient cars,” said California Governor Edmund G. Brown Jr. “This phalanx of states will defend the nation’s clean car standards to boost gas mileage and curb toxic air pollution.”

“The evidence is irrefutable: today’s clean car standards are achievable, science-based and a boon for hardworking American families. But the EPA and Administrator Scott Pruitt refuse to do their job and enforce these standards,” said California Attorney General Xavier Becerra.

“The standards we are fighting to protect were adopted in 2012 and don’t take effect until 2022. They were a lifeline thrown to an industry that was in trouble and desperate for stability. They were based on the best judgment of engineers about what technology could achieve. And in fact they are being achieved today, years ahead of the deadlines, because of the good work of the auto industry,” said California Air Resources Board Chair Mary D. Nichols.

“But now Administrator Pruitt, based on no new information or facts, wants to roll back all that progress in the name of deregulation. The Final Determination is just the first step but it is intended to provide the legal basis for a decision that has already been made: to halt the progress that regulators and industry have made toward a new generation of vehicles. It does not withstand scrutiny and it will not stand.”

Beginning in 2010, the U.S. EPA, National Highway Traffic Safety Administration and California Air Resources Board established a single national program of greenhouse gas emissions standards for model year 2012-2025 vehicles.

Last year, under the Obama administration, the U.S. EPA affirmed these standards were appropriate based on an extensive record of data. The California Air Resources Board also affirmed the standards were appropriate and that the federal government should continue to support a single national program for all states.

On April 13, 2018, however, the U.S. EPA, under the Trump administration, reversed course and claimed that the clean car standards for model years 2022-2025 should be scrapped. The federal government offered no evidence to support this decision and the forthcoming rulemaking intended to weaken the existing 2022-2025 standards, the California governor’s office said.

The federal standard the states are suing to protect is estimated to reduce carbon pollution equivalent to 134 coal power plants burning for a year, and save drivers USD 1,650 per vehicle. The car industry is on track to meet or exceed these standards, Brown’s office added.

A proposal to roll back U.S. federal fuel-efficiency standards for automobiles and light-duty trucks starting in 2021 and challenge California’s ability to establish its own fuel-efficiency standards has been drafted by the U.S. Department of Transportation’s National Highway Traffic and Safety Administration (NHTSA), according to a report by The Washington Post last week.

California was given a waiver under the U.S. Clean Air Act to set its own tailpipe emissions limits. The state’s tougher standards have led automakers to build more fuel-efficient automobiles than required by federal law to allow them to market their vehicles in California. Other states are also allowed to adopt California’s standards, and a dozen currently do. Altogether, these states account for more than a third of the total cars and trucks sold in the United States.

The current administration’s proposal would revoke the ability of any state, including California, to impose different standards from Washington.

The agencies plan to submit the proposal to the White House for review within days, it was reported. The plan would freeze fuel economy targets at the levels required for vehicles sold in 2020, and leave those in place through 2026. If approved, this would represent a major setback to get the average fuel economy of cars and light trucks to 55 miles per gallon (mpg) by 2025. Instead, average vehicle fuel economy would stall at 42 mpg.