Takeaways
- Congress’ recent disapproval of the Biden EPA Clean Air Act preemption waiver for California’s Advanced Clean Cars II and Omnibus vehicle emission standards have prompted California to promulgate emergency regulations reinstating its prior vehicle standards.
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While litigation is pending on the validity of the federal actions disapproving California vehicle emissions laws, CARB’s emergency regulations are intended to address the ongoing uncertainty among manufacturers, fleet operators, logistics companies and other entities subject to California’s vehicle emission standards.
California’s Air Resources Board (CARB), the state’s primary environmental regulator for air quality, has proposed adoption of an emergency rule that would attempt to restore certain vehicle emissions standards in place prior to federal actions earlier this year disapproving California’s Advanced Clean Cars II (ACC II) and Omnibus vehicle emission standards. CARB asserts that the rulemaking is necessary to confirm that the previous vehicle emissions standards remain valid and enforceable during the pendency of ongoing litigation with the Trump administration over the legality of the Congress’ disapproval of California Clean Air Act (CAA) waivers allowing the ACC II and Omnibus regulations. CARB issued a Notice of Proposed Action (NOPA) for the emergency regulations on September 13, 2025.
CARB’s use of the emergency rulemaking process allows the agency to circumvent certain procedural steps ordinarily required for adoption of new regulations, including normal public notice and comment periods, on the grounds that immediate action is necessary to prevent harm to the public from health risks associated with air emissions. CARB’s primary goal, as expressed in the proposed rulemaking, is to maintain vehicle emissions requirements already in effect or planned to go into effect at the time of Congress’ disapproval of the California CAA waivers.
Under the CAA, the U.S. Environmental Protection Agency (EPA) has exclusive and preemptive authority to set nationwide air pollution limits for vehicles; however, the CAA provides California the opportunity to establish more stringent standards if EPA grants a waiver of CAA preemption. This CAA provision was originally adopted to allow California to continue promulgating and enforcing its own stricter vehicle air pollution standards, which had predated the CAA, to address perceived unique and significant adverse air quality conditions in the state. Once granted by EPA, a waiver also allows other states to choose between either the EPA standards or California’s more stringent standards, and several other states have adopted California’s standards.
CARB’s emergency rulemaking comes as a response to two significant actions concerning California’s authority to enforce its own vehicle emission standards. First, on May 22, 2025, Congress adopted three resolutions purporting to disapprove waivers previously granted to California by EPA related to clean vehicle regulations. The State of California, along with 10 other states, subsequently filed a lawsuit on June 12, 2025, against EPA and President Donald Trump to challenge these resolutions. Second, in separate litigation, the U.S. Department of Justice (DOJ) filed two complaints against CARB on August 13 and 14, 2025, regarding the state’s enforcement of emissions standards for heavy-duty trucks and light-duty vehicles, which the DOJ alleges are preempted by the Clean Air Act. CARB asserts that the actions create uncertainty as to what vehicle emissions standards remain enforceable and in effect, prompting the emergency rulemaking.
The ongoing litigation and emergency regulations have created a great deal of uncertainty for manufacturers, fleet operators and logistics companies subject to these regulations. CARB’s emergency rule is intended to preserve regulatory continuity but may also prompt further legal challenges. Pillsbury is able to assist with assessment of regulatory exposure and preparation of compliance strategies under both the California and Federal frameworks.
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