California Withdraws EPA Waiver Request for Advanced Clean Fleets Regulations

On January 13, 2025, the California Air Resources Board (CARB) withdrew its request for a waiver and authorization from the Environmental Protection Agency (EPA), pursuant to Sections 209(b) and (e) of the Clean Air Act (CAA) for its Advanced Clean Fleets (ACF) regulations. CARB initially submitted its request for a waiver and authorization, also called a preemption waiver, on November 15, 2023.

The ACF regulations seek to achieve a fully zero-emission medium- and heavy-duty vehicle fleet in California by 2045 where feasible by requiring a phased transition of fleets to zero-emission vehicles. The regulations provide for this transition to begin in 2025 and continue until no internal-combustion trucks would be sold in California after 2035, as detailed here.

While EPA recently granted other CARB preemption waivers (see EPA’s decision to grant CARB’s Advanced Clean Car II Preemption Waiver), EPA had not yet decided on the request for the ACF regulations. CARB’s decision to withdraw the ACF request for waiver and authorization comes in advance of the change in administration next week.

Statutory and Regulatory Framework

Title II of the CAA assigns the federal government responsibility for regulating emissions from new motor vehicles. Under Section 209(a) of the CAA, states are prohibited from adopting or enforcing any standard related to the control of emissions from new motor vehicles. However, Congress provided an exception to this preemption in § 209(b), which allows EPA to grant California a waiver to set its own emission standards under specific conditions.¹ 

To obtain a waiver, California must determine that its standards “will be, in the aggregate, at least as protective of public health and welfare as applicable Federal standards,” and EPA must deny the waiver if it finds that California’s determination is arbitrary and capricious, California does not need its standards to meet “compelling and extraordinary” conditions, or the standards are inconsistent with CAA § 202(a).²

Advanced Clean Fleets

On November 15, 2023, CARB notified EPA that it had finalized the ACF regulations, which became effective under state law on October 1, 2023, and requested that EPA grant a Section 209(b) waiver. EPA sought public comment on whether the ACF regulations satisfied the applicable waiver criteria and held multiple virtual public hearings. While CARB’s waiver request was pending before EPA, CARB notified the public that it would not take enforcement action regarding the drayage or high-priority fleet reporting requirements or registration prohibitions until EPA grants the preemption waiver or determined that a waiver is not necessary.³ However, CARB encouraged fleets to voluntarily report and comply while the waiver request was pending and “reserve[d] all of its rights to enforce the ACF regulations in full for any period for which a waiver is granted or for which a waiver is determined to be unnecessary.”⁴ Both the drayage truck and high-priority fleet requirements had compliance deadlines beginning as early as January 1, 2024.

During this period, multiple litigation challenges were also filed against the ACF regulations that are still pending in California courts.

CARB’s letter to EPA withdrawing the request and EPA’s subsequent confirmation, available here, do not describe CARB’s position regarding its enforcement notice or the ongoing litigation.

Transport Refrigeration Units

EPA partially approved a preemption waiver for CARB’s amended transport refrigeration unit (TRU) regulation on January 10, 2025, which requires that TRUs use refrigerants with a low global warming potential and for nontruck TRUs to meet particulate matter standards. However, EPA did not act on the portion of the regulation that would have required a phased transition of TRU fleets to 100% zero-emission TRUs by 2029, specified in Cal. Code of Regs. Tit. 13, Section 2477.5(b). Similar to its move with the ACF regulations, CARB withdrew its waiver request for this zero-emission TRU component of the TRU regulation.

Industry Response and CARB’s Next Steps

As of the date of this publication, CARB has not issued further guidance on how the decision to withdraw its request for waiver and authorization will affect its implementation of the regulations or enforcement of the requirements. In the coming weeks, carriers that have made investments in zero-emission vehicles will be weighing the costs of further investments against the likelihood that CARB will abandon mandatory fleet electrification in any future regulations. Carriers that have not yet made investments will weigh the likelihood that CARB may still attempt to enforce certain components of the regulations despite not obtaining an EPA waiver. Overall, fleets will need to be on the lookout for any forthcoming indications from CARB about its ACF enforcement. Sidley will continue monitoring for any further information published by CARB related to the ACF regulations and any requirements that may replace the ACF regulations.

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¹See 42 U.S.C. § 7543(b).

²Id.

³CARB, Advanced Clean Fleets – ENFORCEMENT NOTICE (December 28, 2023).

⁴Id. at 2.