U.S.: federal government challenges California's Clean Trucks Standards

On August 15, 2025, the U.S. Department of Justice (DOJ) filed two complaints in federal courts against the California Air Resources Board (CARB) seeking to block the state’s enforcement of emissions regulations for heavy-duty trucks.

The Clean Air Act (CAA) prevents states from regulating vehicle emissions unless the Environmental Protection Agency (EPA) grants a waiver. California has received more than 100 of those waivers since 1970, enabling it to adopt stricter air quality standards than those required at the federal level. Under the Biden administration, the EPA granted waivers for two CARB regulations imposing more stringent emissions standards on heavy-duty trucks. For example, CARB rules mandate a 90% redu