Updated May 15: California has agreed to formally repeal much of its controversial Advanced Clean Fleets electric-truck mandate in order to settle more than one legal challenge. At the same time, more states are pulling back on adopting the state's Advanced Clean Trucks rules.

Key provisions of Advanced Clean Fleets already were not being enforced because the state did not get a required waiver from the Environmental Protection Agency under the Biden administration. It withdrew its request for a waiver before President Trump took office in January.

Nebraska Attorney General Mike Hilgers announced the legal settlement. The state had led a coalition of 17 states in challenging the Advanced Clean Fleets rules in court.

Among other things, a press release from the AG’s office explained, the ACF rule targeted any fleet that operated in California, regardless of where the fleet was headquartered. Given California’s large population and access to international ports, the news release said, this rule would have had nationwide effects on the supply chain.

In the settlement, California agreed not to enforce key provisions of the Advanced Clean Fleets rule, affecting what it called "high priority" and drayage fleets, and to start the process to repeal it. 

California regulators also conceded that they cannot enforce California’s 2036 ban on the sale of internal-combustion trucks unless until the ban receives a Clean Air Act preemption waiver from the EPA. Such a waiver looks highly unlikely at this point.

On May 15, NTEA – The Work Truck Association and Specialty Equipment Market Association (SEMA) announced a similar agreement with the state in their suit that was filed in October 2024.

That announcement explained that the lawsuit will be held in abeyance with the courts until the California Air Resources Board formally repeals the regulation as required by the agreement between CARB, the California Attorney General, NTEA and SEMA.

What Is the Advanced Clean Fleets Rule?

Advanced Clean Fleets was the second part of California’s efforts to convert trucking in the state to zero-emission vehicles. 

CARB’s regulations call for all trucks and buses sold by 2036 to be zero-emission and fleets to be fully zero-emission by 2045. 

This was to be accomplished through the Advanced Clean Trucks (ACT) rule, which requires OEMs to sell zero-emission vehicles (as HDT previously reported), and the Advanced Clean Fleets rule, which requires fleets to purchase them on a phased-in schedule.

The Advanced Clean Trucks rules were previously approved by the EPA under the Biden administration in 2023. So far, they are still in force, although the Trump administration and Republican-controlled congress have been trying to find a way to rescind that previous approval.

Advanced Clean Fleets would have ended the sale of new fossil-fuel trucks in 2036 and required large trucking companies to convert their existing medium- and heavy-duty fleets to zero-emission battery-electric or hydrogen fuel cell models by 2042.

ACF has been opposed by the trucking industry for setting unrealistic goals for electric-truck adoption and not considering other emissions reduction alternatives.

In the settlements for the state litigation and the NTEA litigation, the California Air Resources Board agreed to begin a rulemaking to repeal ACF's High-Priority Fleet and Drayage Fleet Requirements. 

Unclear, however, is how this will affect the ACF rules for State and Local Government Fleets, which, affecting only fleets in the state, did not require an EPA waiver.

“This resolution marks a significant win for our members and the entire commercial vehicle industry,” said Steve Carey, NTEA president and CEO. 

“Ultimately, work trucks must be available, capable and affordable. Our concern was never about the goal of cleaner vehicles — it was about how to realistically get there."

What's Going to Happen With Advanced Clean Trucks Rule?

Meanwhile, the Trump administration and the Republican-led Congress are trying to kill off the Advanced Clean Trucks rule and California’s diesel emissions rules, which both had already received EPA waivers under the Biden administration.

The legality of how they are attempting it has been called into question.

As Advanced Clean Trucks comes under fire at the federal level, some states that had planned to adopt California's rules are pulling back, due to regulatory uncertainty and pushback from trucking and other industries that say the rules are unrealistic.

The governors of Maryland, Massachusetts, and this week, Vermont and Oregon, have postponed the enactment of California’s Advanced Clean Trucks regulations. They are among 10 states that used federal waivers to implement California’s clean truck rules. Increasingly, those states have concluded that the rules are not economically or technologically feasible and have chosen to postpone the regulations.

Maryland Gov. Wes Moore blamed the Trump administration's actions to unravel Biden-era EV policies and funding for charging infrastructure, as well as challenges for truck makers to comply.

In Oregon, the memo from the Department of Environmental Quality said truck makers indicate that ACT requirements are too difficult to meet, with some having to limit new internal combustion engine truck sales and educing overall new truck availability.”

Oregon Gov. Tina Kotek, who has supported the rule, blamed the Trump administration for its failure to deliver on commitments previously made for clean-energy funding.

Advanced Clean Fleets Already Was Effectively Dead

In January of this year, shortly before President Donald Trump took office, the California Air Resources Board withdrew its request for the Advanced Clean Fleets EPA waiver, realizing that it would be unlikely to get approval under the new administration.

California's withdrawal of the waiver request meant it could not enforce the Advanced Clean Fleet rules.

In announcing the settlement, Hilgers took credit for helping to kill California’s request for the ACF waiver during the Biden administration, noting that he previously led a 24-state coalition in successfully opposing that request.

What's Next for CARB and ACF?

According to the court filing, the California Air Resources Board staff agreed it will present a proposal to repeal the High-Priority Fleet and Drayage Fleet Requirements of the Advanced Clean Fleets regulation to the Board in a public hearing to be held no later than October 31, 2025. 

If the Board approves the proposed repeal, CARB staff will submit that rulemaking action to California’s Office of Administrative Law for approval no later than August 31, 2026.

CARB also agreed that it will not take any enforcement action under the High Priority Fleet or Drayage Requirements for conduct during the period beginning with the earliest effective date of any of these requirements (November 1, 2023) and ending when CARB or OAL (whichever acts latest) takes final action on the CARB rulemaking.

Nor will CARB enforce the part of the Advanced Clean Fleets regulation requiring 100% zero-emission-vehicle sales in the medium- and heavy-duty categories beginning with model year 2036, until CARB obtains a Clean Air Act preemption waiver from EPA for that regulatory requirement.

Attorneys general from the following states joined the lawsuit against California regulators: Alabama, Arkansas, Georgia, Idaho, Indiana, Iowa, Kansas, Louisiana, Missouri, Montana, Oklahoma, South Carolina, Utah, West Virginia, and Wyoming. Also joining the lawsuit were the Nebraska Trucking Association and the Arizona State Legislature.