The Environmental Protection Agency (EPA) is expected to announce less strict fuel economy rules previously set by the Obama administration.

According to the New York Times, the rollback, which reverses the mandatory near-doubling of the average fuel economy of new vehicles by 2015 to 54.5 mpg, is expected to be confirmed by EPA administrator Scott Pruitt in a Sunday declaration at a Chevrolet dealership event in Washington, D.C.

The event will precede a more detailed proposal with the new requirements with no definitive deadline.

The announcement clashes with California and the California Air Resources Board’s expectations of efficient fuel economy rules. As a result of Pruitt’s anticipated decision, the state is expected to file a lawsuit to counter.

“We are going to do everything that can be done to defend these standards,” said California Attorney General Xavier Becerra in a Reuters interview, “So far, when we have been challenged on environmental standards we have had a good record in court. We haven’t lost a case.”

California has long been one of the nation’s leading zero emission advocates.

In January 2018, Gov. Jerry Brown signed an executive order increasing the number of zero-emission vehicles on California’s roads to 5 million by 2030, an increase over an original proposal calling for 1.5 million ZEVs by 2025.

Also, it leads the county with roughly 50 percent of all hybrid vehicle sales and all fuel cell vehicle sales. Other commitments have also been made to increase charging station infrastructure using state vehicle registration fees and cap-and-trade auction proceeds for rebates.