Maryland, along with 16 other states and the District of Columbia, is suing President Donald Trump's administration, demanding it leave in place vehicle emissions standards adopted under President Barack Obama.
The Environmental Protection Agency last month moved to scrap the standards for cars and "light duty" trucks to be sold in model years 2022-2025. The standards would have required the vehicles average more than 50 miles per gallon by 2025.
In announcing the decision to roll back the requirements, EPA Administrator Scott Pruitt had called the Obama-era standards "politically charged," based on poor assumptions, and simply "too high."
But the states involved in the lawsuit say the decision ignored evidence to support the emissions policy.
"Reversing course in the country's efforts to reduce air pollution from passenger vehicles endangers the health of our children and our environment," Attorney General Brian Frosh said in a statement. "Weakening these common sense standards undermines successful efforts made by states, including Maryland, to combat greenhouse gas emissions."
The lawsuit comes weeks after Gov. Larry Hogan's administration joined leaders of other states in writing to Pruitt expressing "deep concern" for any weakening of vehicle emissions rules. Maryland also recently struck a $33.5 million settlement with Volkswagen over a scandal involving diesel vehicles cheating on emissions tests.
The lawsuit was filed in the U.S. Court of Appeals for the District of Columbia Circuit, led by California officials.
Attorneys general in Connecticut, Delaware, Illinois, Iowa, Maine, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, and the District of Columbia also signed off on it. Minnesota state agencies have also endorsed the lawsuit.