On Thursday, the White House released a joint statement with the Environmental Protection Agency (EPA) and the Department of Transportation (DOT), saying that the executive branch would no longer work with California's air regulator to find a middle ground on vehicle fuel-efficiency rules.

The state regulator, called the California Air Resources Board (or CARB), has enjoyed a legal waiver since the 1970s to set more stringent fuel-efficiency standards than those set by the EPA. Generally, automakers find that they must follow CARB's more stringent standards because the vehicle market in California is so huge. But the Trump administration has been working to weaken vehicle fuel efficiency, and CARB's exemption is preventing the administration from fulfilling that campaign promise.

In August, the Trump administration announced the Safer Affordable Fuel-Efficient (SAFE) Vehicles Act. SAFE proposed to freeze Obama-era fuel-efficiency standards—which would gradually make passenger vehicles more efficient until 2025—at 2020 levels. The Trump EPA claimed that the old rule would kill people, because efficient vehicles are more costly, so people put off buying newer, safer cars.

But that line of reasoning was widely panned as flawed by vehicle-efficiency researchers, not only because of what we know about how pollution from vehicles kills people but also because the report that backed up the SAFE Act was methodologically flawed.

The SAFE Act also included wording to eliminate CARB's waiver to set its own fuel-efficiency standards. California, with its history of city-choking smog, has vowed to fight the relaxation of the rules and fight the revocation of its waiver.

“Negotiations”

CARB and the Trump administration had been negotiating to find a middle ground before the administration moves to complete the new rules by March. According to The Wall Street Journal, negotiations had not been going well.

The White House's joint statement said today that "the Trump administration has decided to discontinue discussions with the California Air Resources Board (CARB) regarding the proposed Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule."

"Despite the administration's best efforts to reach a commonsense solution, it is time to acknowledge that CARB has failed to put forward a productive alternative since the SAFE Vehicles Rule was proposed," the statement continued. "Accordingly, the administration is moving forward to finalize a rule later this year with the goal of promoting safer, cleaner, and more affordable vehicles."

According to The Hill, CARB Chairwoman Mary Nichols said earlier this week that negotiation with the Trump administration "never started, so it's easy to end."

"While we have had several meetings with the administration, they were highly non-substantive, and discussion never rose to the level where they could even be called 'negotiations,'" Nichols added. CARB has threatened legal action if the Trump administration rescinds the state's long-standing fuel-efficiency waiver. At least 16 states have pledged to follow CARB's fuel-efficiency standards, despite the EPA's new rule announcement, suggesting the Trump administration is up for a legal fight with more states than California.

Update, 3:40 pm ET: In a statement, CARB chairwoman Mary Nichols responded to the Trump Administration's announcement saying, "It is unfortunate that the Trump administration has chosen to put an end to any effort to find common ground— but it is a signal to us to stand our ground and resolutely defend standards that clean the air we breathe, fight climate change, and provide certainty to carmakers in a global market moving inexorably toward cleaner, more efficient cars."

"We know—and the Trump administration knows—that the technology to meet effective standards is readily available. Despite our best efforts to suggest ways the current rules could be updated to give more flexibility and reduce compliance costs, the Trump Administration continues with standards that fly in the face of science, logic and any effort to protect public health," Nichols' statement concluded.