What you need to know:  The California Air Resources Board (CARB) permanently adopted the Emergency Vehicle Emissions Regulations that were initially adopted in 2025 as a temporary measure after the federal government purportedly   disapproved California’s waivers for newer vehicle emissions regulations, including Advanced Clean Cars II (ACC II) and Heavy-Duty Engine and Vehicle Omnibus (Omnibus). The amendments clarify that California’s earlier emissions regulations will remain in-place.   
 

SACRAMENTO — The California Air Resources Board (CARB) today permanently adopted the Emergency Vehicle Emissions Regulations which had previously been adopted in 2025 as a temporary measure. The temporary action was in response to the unprecedented federal assault on some of California’s vehicle emissions regulations. The amendments confirm that earlier vehicle emissions regulations remain in-place. 

Last year, the federal government purportedly disapproved the U.S. Environmental Protection Agency's (US EPA) previous decisions to grant California waivers to implement newer regulations that are critical for reducing air pollution, including ACC II and Omnibus. The state is challenging the federal government’s actions in court. 

"Despite the illegal and misguided actions of the federal government to subject Californians to the very real hazards of air pollution, CARB is taking action to ensure that vehicle emissions continue to be held to the same standards required in previous years. This action will maintain decades of hard-won improvements to new vehicles and engines sold in California, while providing regulatory certainty for manufacturers, stability in the consumer market and protection of public health," said CARB Chair Lauren Sanchez. 

Specifically, the emergency regulations clarify that vehicle and engine manufacturers may continue to seek CARB certification to the emission standards and requirements that were in effect prior to the adoption of ACC II and Omnibus regulations. US EPA waived preemption for these earlier regulations in actions not targeted for disapproval.  

Manufacturers may also voluntarily comply with ACC II and Omnibus requirements. Doing so provides further regulatory certainty that they remain in compliance with California law in the event the court agrees the federal government's purported disapproval of certain California waivers was unlawful. Manufacturers may also benefit in other ways, including through state procurement preferences and other state-funded programs. 

 
Why it matters  

California suffers from some of the most severe air pollution and associated health impacts in the nation, with motor vehicles and engines being the largest single contributor of smog-forming and toxic emissions. California remains steadfast in its  commitment to protect public health and the environment while working closely with the regulated community.  

This action provides manufacturers flexibility and certainty in this time of unprecedented market and regulatory disruption while also preserving emissions benefits realized under the state’s earlier regulations.