On July 29, 2025, the EPA proposed a rule to rescind its 2009 endangerment finding that carbon dioxide and other chemical emissions from motor vehicles contribute to greenhouse gas pollution and, ultimately, threaten public health and welfare. The finding formed the basis for establishing and implementing greenhouse gas standards for vehicle emissions at the federal level.
The proposed rule would also rescind greenhouse gas emissions standards for light-, medium-, and heavy-duty vehicles. It was published in the Federal Register on August 1, with virtual public hearings planned for August 19–20 and a September 15 comment deadline. If adopted, the rule is likely to face legal challenges based on potential inconsistencies with established precedent, scientific justification, and longstanding agency practices.
California Vehicle Emissions Authority Under Threat
Adding further uncertainty to the future of vehicle emissions standards, President Trump, on June 12, signed three Congressional Review Act (CRA) resolutions aimed at blocking California from enforcing some of its landmark vehicle emissions regulations.
The congressional resolutions reversed EPA waivers granted between 2023 and early 2025 that had allowed California to proceed with its Advanced Clean Cars II (ACC II), Advanced Clean Trucks, and Omnibus Low NOx rules, which have been adopted by multiple other states aiming to reduce air pollution and greenhouse gas emissions. By invoking the CRA – a statute that allows Congress to repeal certain agency actions by simple majority vote – the resolutions invariably declared the California programs preempted and unenforceable.
Earlier this year, the implementation of California’s ambitious Advanced Clean Fleets regulation was partially paused when the California Air Resources Board (CARB) withdrew its request for a federal waiver. While CARB is “evaluating next steps,” (which may be informed by the outcome of pending litigation against the regulation), this move effectively signaled the abandonment of the regulation as it applied to certain fleet categories such as large commercial fleets and drayage trucks. However, the revocation of the waiver carries implications beyond California, particularly for states that have adopted some or all of the related emissions regulations.
States Challenge CRA Actions in Court
In a direct response to the CRA resolutions, a coalition of 11 states – including California, Colorado, and New York – filed a federal lawsuit on June 12, arguing that Congress overstepped its legal authority. The complaint, filed in U.S. district court, asserts that EPA waiver decisions are not the kind of “rules” subject to repeal under the CRA. Instead, they are adjudicatory determinations granted only after a detailed factual and legal review, a process the plaintiffs argue cannot be undone through simple legislative override.
The lawsuit emphasizes that the CRA has never been used to revoke Clean Air Act waivers, which have long recognized California’s distinct air quality challenges and technical leadership. The plaintiffs argue the revocations undermine state sovereignty and violate the Constitution’s separation of powers doctrine. They also argue that prior interpretations from the EPA, the Government Accountability Office, and the Senate parliamentarian all supported the view that these waivers fall outside the CRA’s reach.
While the case proceeds, California Governor Gavin Newsom has directed CARB, through an executive order (also signed on June 12) to begin developing new state-level ZEV rules to help preserve the state’s clean air and climate goals.
Looking Ahead
Federal preemption under the Clean Air Act may prohibit enforcement of state vehicle emissions regulations without a waiver, but it does not automatically invalidate them. As a result, California’s ACC II, Advanced Clean Trucks, and Advanced Clean Fleets regulations may remain on the books under state law. The revocation of federal waivers, however, appears to have introduced significant uncertainty around enforcement authority and long-term compliance – particularly for industry stakeholders in transportation, logistics, and vehicle manufacturing.
Taken together, the CRA rescissions, multistate defense of the EPA waivers, and mounting industry litigation pose a fundamental challenge to California’s longstanding authority to set stricter vehicle emissions standards. While regulatory requirements for fleets and manufacturers remain unchanged, these growing legal disputes could significantly impact how ZEV policies are implemented in the near term.
If you have any questions, or would like additional information, please contact one of the attorneys on our Environment, Land Use & Natural Resources team.
You can subscribe to future advisories and other Alston & Bird publications by completing our publications subscription form.