President Donald Trump says his administration is revoking California’s authority to set auto mileage standards stricter than those issued by federal regulators. In a tweet, Trump said his move would result in less expensive and safer cars. He insisted that new cars would be cleaner, even as they burn more gasoline than they would have under Obama-era fuel efficiency standards he wants to replace. California’s authority to set its own, tougher emissions standards goes back to a waiver issued by Congress during passage of the Clean Air Act in 1970.

Even before the announcement revoking that authority, California and environmental groups said they planned legal action. California officials and environmental groups are criticizing the Trump administration’s decision to revoke the state’s authority to set auto mileage standards. California has long pushed automakers to adopt more fuel-efficient passenger vehicles that emit less pollution. A dozen states and the District of Columbia follow California’s fuel economy standards.

The Trump administration asserts that only the federal government has the power to regulate greenhouse gas emissions and fuel economy.