On May 22, 2025, the U.S. Senate voted 51–44 to rescind California’s authority to enforce its Advanced Clean Cars II (ACC II) regulation, which mandated all new light-duty vehicles sold in the state be zero-emission by 2035.

With the bill expected to be signed into law by President Donald Trump, it would revoke the EPA waiver allowing California and 11 other states to set stricter emissions standards than the federal level.

Industry groups praised the rollback as a move toward a more balanced regulatory environment, while California leaders vowed to challenge the decision in court, citing states’ rights under the Clean Air Act.

Unless blocked by an injunction, the law will take immediate effect, ending enforcement of ACC II in affected states.

Although the California Air Resources Board (CARB) retains control over in-use emissions and specialized programs, the law weakens the scope of CARB’s Advanced Clean Fleets (ACF) regulation by eliminating enforcement of its private fleet mandates.