Providing congressional disapproval under chapter 8 of title 5, United States Code, of the rule submitted by the Environmental Protection Agency relating to "California State Motor Vehicle and Engine and Nonroad Engine Pollution Control Standards; The 'Omnibus' Low NOX Regulation; Waiver of Preemption; Notice of Decision".

This law overturns an Environmental Protection Agency decision that had granted California permission to enforce stricter nitrogen oxide (NOX) emissions standards for heavy-duty vehicles and engines. The EPA had approved California's request for a waiver under the Clean Air Act, which normally reserves vehicle emissions regulation to the federal government. California's "Omnibus" Low NOX regulation aimed to reduce nitrogen oxide emissions from heavy-duty trucks and engines by approximately 90 percent compared to federal standards.

By nullifying this EPA approval, the law prevents California from enforcing these stricter emissions standards. It also blocks other states that had adopted California's standards from enforcing them as well. The law was passed through the Congressional Review Act, a procedure that allows Congress to disapprove federal agency actions. Under this law, the EPA is prohibited from approving future waivers that are substantially similar to the one that was disapproved.

The practical effect is that heavy-duty vehicle emissions standards will remain at federal levels rather than the stricter California standards. Supporters argued this protects consumers from higher vehicle costs and preserves choice in the types of vehicles Americans can purchase. Opponents contended the law eliminates important air quality protections and health benefits that the California standards would have provided.

This law became effective upon the President's signature on June 12, 2025. It applies nationwide, affecting manufacturers, trucking companies, and consumers who purchase or use heavy-duty vehicles. The law does not affect California's other existing emissions waivers or regulations that were approved under different Clean Air Act provisions.