Under the California Advanced Clean Fleets settlement reached in May 2025, the California Air Resources Board agreed to repeal the heart of its Advanced Clean Fleets regulation: the mandates that would have forced private trucking fleets and port drayage operators to transition to zero-emission vehicles. CARB also conceded it cannot enforce the rule’s 2036 ban on new combustion truck sales without an EPA preemption waiver it does not have. The requirements covering state and local government fleets survive, though on a slower timeline.
What CARB Agreed to Do
Chief District Judge Troy L. Nunley signed the stipulation and order on May 2, 2025, in the case brought by a Nebraska-led coalition of states in the U.S. District Court for the Eastern District of California. Nebraska Attorney General Mike Hilgers announced the settlement publicly on May 6, 2025.
The agreement set three operative deadlines for CARB:
- Present a proposal to repeal the high-priority and drayage fleet requirements at a public hearing by October 31, 2025.
- Submit the completed rulemaking to California’s Office of Administrative Law by August 31, 2026.
- If the Office of Administrative Law has not approved the repeal by October 15, 2026, the parties must file a joint statement outlining how to proceed.
CARB also agreed not to enforce any of the high-priority or drayage fleet requirements for conduct occurring between November 1, 2023, and the date the repeal becomes final. That no-enforcement window matters because CARB had previously reserved the right to enforce the rules retroactively once an EPA waiver was granted, meaning diesel trucks a fleet added during the wait could later have been forced off the road. The settlement closed that door.
The coalition that secured the deal included Nebraska, Alabama, Arkansas, Georgia, Idaho, Indiana, Iowa, Kansas, Louisiana, Missouri, Montana, Oklahoma, South Carolina, Utah, West Virginia, Wyoming, the Nebraska Trucking Association, and the Arizona State Legislature.
What the Repealed Provisions Required
CARB adopted the Advanced Clean Fleets regulation in April 2023, with an effective date of October 1, 2023. Two of the three fleet categories it covered are the ones being repealed.
High-priority fleets, defined as companies with more than 50 trucks or over $50 million in annual revenue, were required to begin purchasing only zero-emission trucks for new additions starting in January 2024, or alternatively to meet specific percentage targets for fleet composition under a milestone schedule. Internal combustion vehicles had to be retired after reaching 13 years, 800,000 miles, or 18 years of age.
Drayage fleets, the trucks serving California’s ports and intermodal rail yards, had to register new entrants as zero-emission starting January 1, 2024, with the entire drayage fleet required to be zero-emission by 2035.
Both provisions needed an EPA preemption waiver under the Clean Air Act before CARB could enforce them against private operators. CARB submitted its waiver request on November 15, 2023. On January 13, 2025, a week before President Trump’s second inauguration, CARB voluntarily withdrew the application, citing uncertainty from the incoming administration. The waiver withdrawal left the private-fleet provisions effectively unenforceable even before the settlement; the settlement locked that outcome into a formal repeal.
The 2036 Sales Ban Concession
Separate from the fleet-purchasing mandates, the Advanced Clean Fleets rule contained a manufacturer-side provision: starting with model year 2036, all medium- and heavy-duty vehicles sold in California would have to be zero-emission. In the settlement, CARB conceded it cannot enforce that requirement unless it first obtains an EPA preemption waiver for that specific provision.
A parallel stipulation CARB reached with the California Trucking Association in April 2025 reached the same result through a different case: CARB agreed not to enforce the 2036 zero-emission sales mandate without an EPA waiver, and the CTA litigation was stayed.
What Survives: Government Fleets
The state and local government fleet requirements were not part of the settlement and remain in effect, because they do not require a federal waiver. CARB has, however, modified them through the same rulemaking that handles the repeal.
The amended rules extend the 50% zero-emission purchasing requirement for government fleets by three years, pushing the window from 2024–2026 to 2024–2029. The 100% zero-emission purchasing mandate moves from 2027 to January 1, 2030. Small agencies with 10 or fewer vehicles in certain counties receive additional extensions.
One point of continued contention: CARB has maintained that private companies operating under contract for government entities still count as part of those entities’ fleets, a position that drew over 200 opposition comments during the rulemaking.
Where the Repeal Stands
CARB moved through the repeal process faster than the settlement required. On September 25, 2025, the Board voted to repeal the drayage, high-priority, and federal fleet requirements from the California Code of Regulations. CARB issued a 15-day notice of modified text on April 2, 2026, with a public comment period closing April 17, 2026. A second round of proposed revisions was published on June 1, 2026, with comments due June 16, 2026. Final submission to the Office of Administrative Law is due by August 31, 2026.
CARB has signaled that its new approach to heavy-duty vehicle emissions will come through an initiative called “Drive Forward,” which combines incentive funding, market outreach, and infrastructure planning rather than purchase mandates. New regulatory proposals under that framework are not expected for several years.
The Fights the Settlement Did Not End
The settlement resolved the Advanced Clean Fleets dispute, but it did not end the broader conflict over California’s authority to set vehicle emission standards, and a reader relying on the settlement alone would miss what came next.
On June 12, 2025, President Trump signed three congressional joint resolutions under the Congressional Review Act revoking EPA waivers the Biden administration had granted for California’s separate Advanced Clean Trucks rule, its Advanced Clean Cars II program, and its heavy-duty low-NOx omnibus rule. EPA Administrator Lee Zeldin stated that the Congressional Review Act bars the EPA from approving future waivers that are “substantially the same” as those revoked. California, joined by ten other states, sued the federal government in the U.S. District Court for the Northern District of California, arguing the Congressional Review Act does not apply to EPA waiver decisions. That case remains pending. Governor Newsom signed Executive Order N-27-25 the same day the resolutions were signed, directing CARB to develop a backup “Advanced Clean Cars III” framework.
A second active front involves the Clean Truck Partnership, a July 2023 voluntary agreement in which major truck manufacturers committed to meeting California’s emissions standards regardless of waiver status in exchange for implementation flexibility. After the federal waiver revocations, Daimler Truck North America, International Motors, Paccar, and Volvo Group North America sued CARB on August 13, 2025, seeking to invalidate the agreement; the U.S. Department of Justice intervened as a plaintiff. CARB responded with a breach-of-contract suit in Alameda County Superior Court in October 2025. On October 31, 2025, the federal court granted a partial preliminary injunction blocking CARB from enforcing the partnership, finding the manufacturers faced “concrete and nonspeculative irreparable harm.” A summary judgment hearing is set for August 7, 2026.
Other states that had been following California’s lead on clean truck rules have also pulled back. Governors in Maryland, Massachusetts, Vermont, and Oregon postponed enactment of Advanced Clean Trucks requirements, and Washington, Vermont, and Oregon took steps to halt enforcement of ACT or Advanced Clean Cars II obligations. No state outside California had formally adopted the Advanced Clean Fleets regulation, so the repeal itself has no direct effect on other states’ books; the ripple is running through the related rules instead.