The Trump administration could move at any time to revoke California's right to impose stricter auto emissions standards than the federal government does, and the state's senators are already mounting a fight.
Congressional sources are hearing conflicting information on whether and when the Environmental Protection Agency will revoke California's waiver.
Initially the EPA action appeared imminent, but now there is some uncertainty, in part because the action would set up a legal showdown with California that President Donald Trump could lose.
The EPA is refusing to comment, with a spokeswoman saying, "We don't have any information to offer at this time."
California has signaled its willingness to fight Trump in court and has hired former Attorney General Eric Holder to assist with challenges to the president's policies.
No administration has tried to revoke an existing waiver issued under a Clean Air Act for California to set its own auto emissions standards. So there is no legal precedent for how a judge could rule, said Richard Frank, an environmental law processor at the University of California, Davis.
"It would be somewhat difficult and legally suspect for the Trump administration to try and withdraw a waiver that has been previously granted," Frank said.
Sen. Kamala Harris, D-Calif., said she'd been fearing EPA action since agency chief Scott Pruitt told her at his January confirmation hearing that he planned to review the waiver.
Harris noted in a Thursday interview that Pruitt was a champion of state sovereignty as Oklahoma's attorney general before Trump picked him to lead the EPA.
Now, Harris said, he is looking at telling California that it cannot enforce its own vehicle pollution standards.
"You can't talk out of both sides of your mouth," said Harris, a former attorney general of California.
Sen. Dianne Feinstein of California joined nine other Senate Democrats and Sen. Bernie Sanders, a Vermont independent, in a letter calling on Pruitt to keep auto pollution standards in place. Trump is expected to roll back the national fuel economy standards that were imposed during the Obama administration in line with California's rules.
The standards "enhance our national security by reducing our consumption of foreign oil. They will benefit consumers, saving them billions of dollars at the pump, and reduce our carbon pollution. It is critical that they remain in place," Feinstein and the other senators wrote.
The automotive industry has been lobbying against the rules, calling them too expensive. Automakers have written letters to the Trump administration saying the standards will be difficult to hit and will force them to produce more cars with higher gas mileage when less-fuel-efficient sport utility vehicles, trucks or larger cars are more popular.
California's ability to set its own auto pollution rules has been a centerpiece of its efforts to combat global warming. California has used the waiver to pressure auto manufacturers to build more efficient vehicles. Harris said the rules had been effective in creating a cleaner environment in the state.
"I'm very concerned. And remember that issues affecting California's consumers affect people around the country, especially when you are talking about auto emissions standards. Because we have almost 39 million people," Harris said. "The industry, in needing to conform to the California standards, has to then adapt, usually, their standards for everyone else."
Trump has made the auto industry a major focus since taking office, saying environmental rules are "out of control."
California started regulating air pollution in the 1960s before the federal Clean Air Act of 1970 was passed. The state has since received federal waivers to enact its own pollution rules, including tailpipe standards, which are stronger than the national rules.
The EPA has consistently granted California the waiver over the years. An exception was 2008, when the George W. Bush administration denied the waiver only to have the Obama administration approve it a year later.
A dozen states, including Massachusetts, have been allowed to adopt the stricter California standards.
"Attacking the California waiver is a recipe for chaos," said Sen. Edward Markey, D-Mass.
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