It has all the makings of a legal prize fight: In the red corner, the Trump administration, backing auto manufacturers that argue vehicle fuel efficiency standards will cost billions of dollars. In the blue corner, the state of California, which is determined to press ahead with its plans to curb gas guzzlers and promote electric vehicles.

The Trump administration is expected shortly to announce a review of Obama-era federal standards that require car makers to increase the average fuel efficiency of new vehicles to 54.5 miles per gallon by 2025. The Environmental Protection Agency may also attempt to revoke legal waivers that allow California to set its own tougher standards on fuel efficiency and the adoption of electric vehicles. These standards can then be followed by other states instead of those set by the federal government.

US car dealers expect to sell more than 17 million new vehicles this year. Right now, states that follow California’s lead account for about a third of the market for new cars, SUVs, and pickup trucks. This means the Golden State can force the auto industry to roll out cleaner vehicles — whatever happens at the federal level.

“If automakers want to play in one-third of the market, they need to comply with California’s regulations,” David Keith of the MIT Sloan School of Management, an expert on technology adoption in the industry, told BuzzFeed News.

Any attempt by the Trump administration to remove California’s current waivers is sure to spark a legal fight. “That’s a major assault on California’s sovereignty,” Ethan Elkind, who heads the Climate Change and Business Program run by the law schools at the University of California, Berkeley, and UCLA, told BuzzFeed News.

It’s a fight that auto manufacturers are urging the federal government to take on. In January, Ford CEO Mark Fields told Donald Trump in a meeting at the White House that federal fuel efficiency standards risk more than a million American jobs.

That conclusion comes from an industry-backed analysis that critics argue is seriously flawed. Still, nobody disputes that the car market has changed since the standards for model years from 2017 to 2025 were set back in 2012, when gas averaged $3.60 a gallon. Today, it’s $2.31.

“One of the major surprises has been gasoline prices are lower than we thought they’d be,” Joshua Linn, an energy economist with Resources for the Future (RFF), an independent think tank in Washington DC, told BuzzFeed News.

Low gas prices not only encourage people to drive more, they also change the vehicles that are sold. The market for SUVs and pickup trucks is now booming, with many consumers opting for high-performance, gas-guzzling models.