The Biden administration today approved California’s groundbreaking mandate phasing out new gas-powered cars just weeks before the incoming Trump administration poses a threat of overturning electric vehicle and climate rules.

The granting of the waiver by the U.S. Environmental Protection Agency allows California to move forward in requiring 35% of new 2026 model cars sold in the state to be zero-emissions, 68% in 2030 and 100% in 2035.

The EPA also today gave the go-ahead to a 2020 California regulation requiring reductions in nitrogen oxides — a key ingredient of smog — emitted by heavy-duty trucks and buses.

The Trump administration is likely to challenge the approved waivers through the courts and deny other California vehicle standards yet to be greenlit.

At a campaign event in Michigan earlier this year, Trump dismissed the possibility of any state banning new gas-powered cars, declaring, “I guarantee it — no way.”

For longer than half a century, California’s vehicle emissions rules have been the driving force for dramatic improvements in the state’s air quality, especially in the smoggy Los Angeles basin and San Joaquin Valley. Cars, trucks and other vehicles are the biggest sources of smog-forming gases and soot, which cause asthma and heart attacks and other serious respiratory problems.

“California has longstanding authority to request waivers from EPA to protect its residents from dangerous air pollution coming from mobile sources like cars and trucks,” EPA Administrator Michael S. Regan said in a statement. “Today’s actions follow through on EPA’s commitment to partner with states to reduce emissions and act on the threat of climate change.”

Congress granted California the authority to set its own vehicle emissions standards in a 1967 clean-air law. But each standard set by California requires a waiver from the EPA before it can be implemented.

“California has longstanding authority to request waivers from EPA to protect its residents from dangerous air pollution coming from mobile sources like cars and trucks.”
— EPA Administrator Michael S. Regan

Under the federal Clean Air Act, the EPA can only legally reject a waiver if it’s “arbitrary or capricious,” unnecessary for addressing air pollution or technologically infeasible due to inadequate lead time.

None of EPA waivers to California has ever been revoked. But the Trump administration in 2019 attempted to revoke one that the Obama administration granted for California’s 2012 zero-emission car mandate. The Biden administration, however, reinstated it in 2022, which has triggered lawsuits by oil companies and Republican-led states.

The stakes are high since the state’s air pollution ranks among the nation’s worst. Failure to meet federal health standards for smog and soot could result in economic sanctions, including the loss of highway funds.

“This might read like checking a bureaucratic box, but EPA’s approval is a critical step forward in protecting our lungs from pollution and our wallets from the expenses of combustion fuels,” Paul Cort, an attorney with the environmental group Earthjustice, said in a statement. “The gradual shift in car sales to zero-emissions models will cut smog and household costs while growing California’s clean energy workforce.”

A Hyundai Ioniq 6 charges at an Electrify America charging station in Oakland. Under California’s mandate, 100% of new car sales must be emissions-free in 2035. Photo by Camille Cohen for CalMatters

The Newsom administration has been pressing the EPA this year to approve all eight California clean-vehicle rules that still needed the agency’s go-ahead. Gov. Gavin Newsom traveled to Washington, D.C. last month to press the Biden administration to act before Donald Trump takes over the White House on Jan. 20.

“Clean cars are here to stay,” Newsom said in a statement. “Automakers and manufacturers have made it clear they intend to stick with California and consumers as we move toward clean cars that save people money. Naysayers like President-elect Trump would prefer to side with the oil industry over consumers and American automakers, but California will continue fostering new innovations in the market.”

Nevertheless, the transition to electrify transportation faces headwinds even in the Golden State. Electric car sales, once surging, have plateaued this year. Sales through the first nine months of this year were up only 1.2% over the same period last year, according to state data. That compares to a 56% increase in sales the previous year and 38% in 2022.

The November election has already influenced some decision-making at The California Air Resources Board, which enacts the state’s air pollution and climate rules. Earlier this month, the board at the last minute pulled back a proposed rule ramping up sales of zero-emission motorcycles. That decision came in part due to Trump’s election, a person familiar with the board’s thinking said. The state will instead offer incentives for people to buy electric motorcycles.

The EPA still is considering six other California clean air rules, including ones that phase out diesel trucks and require cleaner locomotives, commercial ships and off-road diesel vehicles like tractors and construction equipment. The most controversial are the regulations for trucks and locomotives.

Last week, the U.S. Supreme Court decided to review whether the oil industry has the legal standing to try to overturn a lower court’s decision that allowed California to set low- and zero-car emission standards for model years 2015 through 2025.

The new waivers approved today could provide more opportunities for legal disputes in the Trump 2.0 era. Those battles could once again reach the conservative-leaning Supreme Court. The justices earlier this year did away with a 40-year-old judicial rule of thumb, known as “Chevron deference,” which has been key for setting climate and environmental policy. The principle, rooted in a 1984 decision, obligated judges to yield to a federal agency’s interpretation when determining how a Congressional law should be applied.

Congress has passed little direct legislation on climate change and the EPA has relied on interpretations of older environmental laws, including the Clean Air Act.

Efforts to overturn California’s authority may also extend to Congress. The Congressional Review Act allows Congress to revoke federal rules approved during a certain timeframe at the end of an administration. Legal experts, however, debate whether that law would apply to EPA actions related to California’s clean-air waivers.

Republicans may attempt to repeal the Clean Air Act provisions that empower California, but such efforts would likely encounter resistance, including potential Democratic filibusters. Historically, bipartisan support for combating air pollution has thwarted similar moves to alter the Clean Air Act.

California’s clean-car mandate is also central to its climate strategy and has helped make the state a national leader in climate policy, with 11 states and Washington, D.C., adopting or planning to adopt its zero-emission car sales mandate.

The state’s history and economic influence also position it as a formidable opponent. Many automakers, aware of California’s large market share, have opted to negotiate with the state rather than resist. In 2020 BMW, Ford, Honda, Volkswagen and Volvo agreed to adhere to California’s standards through 2026, irrespective of federal actions. Stellantis pledged compliance with zero-emission car sales requirements through 2030, even in the face of federal or judicial opposition.

For 2026 models, 35% of sales in California must be zero emissions under the state rules; through September, they are only 25.4% of sales this year.

The phased-in mandate allows sales of new plug-in hybrids as well as battery-only cars, and the state says some gas-powered cars are expected to remain on California roads for more than 25 years.

Many obstacles stand in the way of electrifying cars, including the need for more public fast chargers. State officials estimate that California needs a million public charging stations in six years — almost 10 times more than the number available to drivers a year ago — and 2.1 million by 2035.

The Alliance for Automotive Innovation, an industry group, published a memo last week saying that it “will take a miracle” for all of the states that follow California’s rules to reach 100% new zero-emission cars by 2035.

“There needs to be balance and some states should exit the program,” the automakers said.

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CalMatters.org is a nonprofit, nonpartisan media venture explaining California policies and politics.