Until EPA decided to cancel California's 2009 waiver for federal rules on emissions out of spite
If you are not aware, if you buy a car in another state you might not be able to bring it to California because California imposes its own restrictions on vehicle emissions, which force California consumers to pay higher prices. But that is illegal so the U.S. Department of Transportation, EPA, and other agencies had to give them a waiver for what would be unfair restriction of trade when they preempt federal fuel economy regulations. (They do it with lightbulbs also. You can't buy a cheaper LED bulb on Amazon even though it is the same efficiency bulb, because the company is not certified by California.)
California Governor Gavin Newsom has been vitriolic toward Republican President Donald Trump - and he is seen to be waffling on putting an end to the anti-vaccine movement that has made California a medical laughingstock to the rest of the country, so he is doing everything wrong for California.
Washington, D.C. seems to have grown tired of the state telling the federal government they are the leaders of the country and Environmental Protection Agency is getting ready revoke the 2009 waiver that allows California to force car manufacturers to spend more, and the U.S. Transportation Department is doing the same, because California forces companies to sell more electric cars in the state each year.
That can only be a punitive response by the federal government to an immature state government. Yes, California Air Resources Board is a rogue agency, they've been busted lying on emissions studies too many times to count, but EPA would let that go if Governor Newsom could keep his mouth shut.
Automakers are willing to make a voluntary compromise on efficiency standards - regulatory certainty is better for companies than uncertainty while scientifiic validity is argued in court - but they may be able to signal they are willing to do so now, while waiting until voters replace legislators with people who are interested in helping California more than they are interested in hurting Republicans.