Mary Nichols, the powerful head of the California Air Resources Board, didn’t even need to explicitly threaten a ban on gas-powered cars last week to get the attention of carmakers.

The warning was only in her prepared statements for a workshop with the state Transportation Commission. But the remarks, obtained by Bloomberg, hit headlines and the industry took notice. That was the point.

Nichols is making it clear that if the Trump administration follows through on threats to hamstring California’s ability to police tailpipe emissions, the state will need to find another way to keep the air clean. That will affect people and industries, including car manufacturers.

At issue is the Trump administration’s proposal to roll back tailpipe emissions and fuel economy regulations that have been on the books for years. Trump’s Environmental Protection Agency would also yank a key waiver that lets California make its own clean air rules and require that auto manufacturers sell a certain percentage of clean cars in the state. The federal proposal hasn’t yet been finalized — and likely will be tied up in court for years. Still, the transportation sector is the number one producer of greenhouse gases in California, and the state is bracing for a hit to its climate goals and air quality.

The potential fallout was the subject of last week’s workshop with the Transportation Commission. Remarks written for the workshop said the rollbacks could force the air board to look for other ways to curb pollution, including “an outright ban on internal combustion engines.” Out loud, however, Nichols spoke more vaguely of “potentially looking at things like fees, taxes and bans on certain types of vehicles and products. And these are not things that most of us think are the right way to go.”

“Ban — it’s not a word that we use”

A ban on gas-powered cars isn’t imminent, Nichols said in an interview with CALmatters this week. “Ban — it’s not a word that we use, and we don’t like to use it,” she said. “But sometimes, we perhaps have to make a point. And the message here was intended to be heard by the auto industry.”

The auto industry initially supported the fuel economy and greenhouse gas standards the Obama administration finalized in 2012. The standards were set through 2025, and a federal review in 2016 reported that industry was technologically on track to meet them. It also projected fuel savings and public health benefits for the public. But when President Donald Trump took office, the auto industry asked the administration to revisit the issue.

Last week wasn’t the first time Nichols had pointed words for the auto industry. At a public meeting in 2017, she asked automakers: “What were you thinking when you threw yourselves upon the mercy of the Trump administration to try to solve your problems?” It’s not even the first time she’s talked about a ban.

Perhaps that’s why when the auto industry heard Nichols’ latest message, it didn’t appear to worry. Gloria Bergquist, vice president of the Auto Alliance trade group, said if the state banned the sale of traditional gas-powered vehicles, the industry would wind up selling more electrified ones. “We’d move them from dealer’s lots and get them into people’s garages. So that’s good — good for automakers,” said Bergquist, who added the automakers she represents have a stake in selling the electrified models they’ve invested in. The concern would be in areas where automakers don’t yet have enough options — like work vehicles, for instance. “There are very few electrified pickups that could do the work that [farmers] need to do,” Bergquist said.

“An untested legal question.”

No matter the action — bans, status quo, or a continued battle with the Trump administration — California can expect to spend time in court to protect its air. But Bergquist declined to speculate whether the auto industry would fight a gas-powered car ban in court. “We haven’t focused on it, just because we think it might have been some hyperbole,” she said.

The threat might not be real now, but it’s not an empty one. Nichols said they could do it, if it came to that. “A requirement for 100% of all sales to be zero emissions vehicles means that no internal combustion engines would be able to be sold after a certain date,” she said.The agency, she clarifies, isn’t proposing to do this right now — but, she said, “It’s something we would have to consider.”

Still, Meredith Hankins, Shapiro fellow in Environmental Law and Policy at the UCLA School of Law, warns it won’t be easy to go through the EPA to make that kind of change. “It may be sort of dead on arrival under this current administration,” Hankins said. And going around the EPA is “an untested legal question.”

While other legal experts agree the air board probably could find a way to ban combustion engines, the question is whether it should. “That would be a very blunt, last resort approach,” Daniel Sperling, director of the Institute of Transportation Studies at UC Davis and a member of the air board, said in an email.

Sperling said he thinks a better strategy would be a legislative one called “feebates,” which use fees to discourage dirty car use, and rebates to encourage people to drive cleaner vehicles. The Legislature has yet to agree. Assemblyman Phil Ting, a San Francisco Democrat, saw his bill to ban registrations of gas-powered vehicles by 2040 die. His second, a watered-down proposal to plan for a clean-car future, stalled as well.

Local officials aren’t waiting for state action. New York City will kick off a toll program to cut downtown traffic in a few years, and Boston and Los Angeles are eyeing similar congestion-pricing initiatives. Smaller cities like Sacramento have increased parking prices and improved light rail. The strategy, Hankins said, makes it too expensive to drive in cities.

These are steps to a world Nichols is shooting for in the next quarter century. “By 2045, there can’t be any cars sold in California that aren’t zero emissions vehicles of one sort or another. I don’t expect to be alive to see that, but that’s where we’re headed.”