A coalition of 17 states and the District of Columbia sued the Environmental Protection Agency on Tuesday, asking a federal court to block a Trump administration attempt to weaken automobile emissions standards.

The states, led by California Attorney General Xavier Becerra, argue that a recent EPA decision to revise the Obama-era emissions rules was made without clear reasoning or evidence to support it and should be struck down.

"The evidence is irrefutable: today's clean car standards are achievable, science-based and a boon for hardworking American families," Becerra said in a statement. "But the EPA and Administrator Scott Pruitt refuse to do their job and enforce these standards."

The standards ratchet up fuel economy requirements for cars and light trucks through model year 2025. In January 2017, before Trump took office, the EPA issued an evaluation for years 2022-2025, saying that the ambitious auto efficiency and greenhouse gas emissions standards were feasible and that the benefits outweighed the costs of implementation.

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But last month, Pruitt announced the agency was withdrawing that determination and would revise the standards. The EPA wrote that it was reversing course because "many of the key assumptions EPA relied upon in its January 2017 Determination, including gas prices and the consumer acceptance of advanced technology vehicles, were optimistic or have significantly changed and thus no longer represent realistic assumptions."

While the Trump administration has yet to announce what it would replace the current standards with, one option reviewed by The New York Times last week would freeze them at 2020 levels. The agency is also expected to revoke California's waiver allowing it to set more demanding standards, which other states may also follow.

Arbitrary and Capricious?

The states that filed suit on Tuesday are asking the U.S. Court of Appeals for the District of Columbia Circuit to rule that Pruitt's reversal was arbitrary and capricious and should be blocked.

A report published Tuesday by the Institute for Policy Integrity at New York University School of Law supports their claim. The report says gasoline price forecasts remain essentially unchanged since the EPA made its first determination, and that purchases of electric and hybrid vehicles remain strong.

"EPA provided no factual basis for its decision to reverse course on emissions standards," Jeffrey Shrader, an economic fellow at the institute, said in a statement. "The data supporting the existing standards is robust, and it has not changed significantly since the agency's thorough review in 2017."

Critical for Cutting Climate-Warming Emissions

The auto standards are arguably the most important single policy for cutting the nation's climate-warming emissions. While emissions from the electricity sector have been falling as natural gas and renewable energy sources replace coal, those from the transportation sector have continued to climb. Transportation is now the single largest source of energy-related carbon dioxide emissions.

California in particular has resisted the Trump administration's attempts to reverse or weaken the emissions rule. The state has adopted ambitious goals to cut its greenhouse gas emissions and likely cannot achieve them unless its automobile fleet becomes more efficient and more electrified.

The coalition that filed suit today includes California, Connecticut, Delaware, Illinois, Iowa, Maine, Maryland, Massachusetts, Minnesota, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, and the District of Columbia. Those jurisdictions represent 44 percent of the nation's population and 43 percent of new car sales, the group says.

"These emission standards are common sense—protecting our air and mitigating our contributions to climate change, all while saving drivers money at the pump," New York Attorney General Eric Schneiderman said in a statement. "Yet the Trump administration conducted a phony study, ignoring the facts and the law in order to cook the books on these critical standards."