In a letter dated January 13, 2025, the California Air Resources Board (CARB) withdrew its request for a Clean Air Act (CAA) waiver for its Advanced Clean Fleet Regulation. The original request sought a waiver to allow the state to enact rules to require all medium- and heavy-duty trucks operating within the Golden State to convert to zero-emission vehicles by 2035.

 

“While we are disappointed that U.S. EPA was unable to act on all the requests in time, the withdrawal is an important step given the uncertainty presented by the incoming administration that previously attacked California’s programs to protect public health and the climate and has said will continue to oppose those programs,” CARB Chair Liane Randolph said in a statement, according to the Los Angeles Times.

Just last month, the Biden EPA announced it granted two requests from CARB for waivers to implement and enforce its Advanced Clean Cars II (ACC II) regulations for light-duty vehicles and its “Omnibus” low-NOx regulation for heavy-duty highway and off-road vehicles and engines.

These are just two of six recent California waivers the Biden EPA administration approved before leaving office.

California waivers

The CAA doesn’t allow states to adopt or enforce emissions standards for new motor vehicle engines or for new motor vehicles.

“However, because California had adopted its own clean air regulations addressing motor vehicle emissions prior to the adoption of the CAA, Section 209(b) allows California to request that the [EPA] waive this preemption so that California can enforce more stringent standards in the state,” notes law firm Holland & Knight LLP. “This process is colloquially referred to as ‘California's waiver.’”

This section of the CAA requires the EPA to grant California’s waivers unless the Agency administrator finds that the state:

• “was arbitrary and capricious in its finding that its standards are, in the aggregate, at least as protective of public health and welfare as applicable federal standards;
• does not need such standards to meet compelling and extraordinary conditions; or
• such standards and accompanying enforcement procedures are not consistent with Section 202(a) of the [CAA].”

At the time the CAA was implemented, California was already way ahead of the federal government in regulating emissions and smog. This is why Congress, under the CAA, provided California with the specific ability to adopt emissions requirements to meet its significant air quality challenges.

The Trump factor

During President Donald Trump’s previous administration, California’s waivers were revoked—a decision Earthjustice says was illegal.

“Representing Sierra Club, Earthjustice sued the EPA and National Highway Traffic Safety Administration in 2020 in separate lawsuits in the D.C. Court of Appeals for the illegal rollback of clean car and fuel economy standards,” Earthjustice says. “The Trump administration’s rule is based on massive technical and economic errors — and fails to meet core legal requirements.”

Trump plans to revoke the California waivers again during his current term, according to POLITICO.

“‘On Day One of the Trump administration, not only will Crooked Joe’s Electric Vehicle mandate be terminated, but any Biden waiver allowing gasoline-powered cars to be outlawed will be immediately revoked,’ Trump campaign national press secretary Karoline Leavitt said in a statement to POLITICO.”

Legal challenges

The Biden administration EPA based its decision to grant the last two California waivers primarily on the need to reduce soot and smog in the Golden State, which are less politically charged issues than greenhouse gas (GHG) emissions.

“The Biden administration tried to be very meticulous in drafting the waiver decisions in a way to best withstand judicial attack,” said Michael Gerrard, founder and faculty director of Columbia Law School’s Sabin Center for Climate Change Law, according to Bloomberg Law.

With Congress expressly granting California the ability to enforce its own emissions standards under the CAA, judicial challenges to take away this authority are unlikely to prevail, analysts predict.

However, Diamond Alternative Energy v. EPA was accepted into the U.S. Supreme Court’s (SCOTUS) docket in December 2024. The case challenges the Biden administration’s regranting of the California ACC waiver.

“The Court granted certiorari on the issue of standing and redressability but did not grant certiorari on the plaintiff's second question regarding the lawfulness of the waiver as a whole,” Holland & Knight says. “The Court also declined certiorari for a second set of plaintiffs in a related action in Ohio v. EPA. That case had asked the Court to opine on the constitutionality of the waiver provision under a state equal sovereignty theory. Another case challenging the waiver for California's Advanced Clean Trucks rule is being held in abeyance in the U.S. Court of Appeals for the D.C. Circuit, pending final decisions in the Diamond Alternative Energy and Ohio cases.

“The state's response – whether it be new rulemaking, holding existing rules for four years and hoping for a more receptive administration, litigation or attempting to enforce rules despite lack of a waiver – will hugely impact anyone who buys or operates motor vehicles in California and elsewhere in the nation.”