In September 2019, the National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) finalized the the Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule Part One: One National Program. In the SAFE Rule Part One, EPA revoked California's authority to set its own greenhouse gas emission standards and zero-emission vehicle mandate under the Clean Air Act.
On April 26, 2021 EPA announced that it was reconsidering the withdrawal of California's preemption waiver and requested comments. EPA will accept comments until July 6 and will hold a virtual hearing on June 2. More information is available here.