Since the birth of the modern Clean Air Act in 1967, California and only California has had the authority to deviate from federal rules to set its own standards for tailpipe emissions from motor vehicles. To be enforceable, California’s standards must be more stringent than federal rules and must be granted an EPA waiver after the agency determines that California faces “compelling and extraordinary” conditions. Other states can then choose between following the federal standards and the California standards.
To date, the EPA says it has granted California about 50 such waivers and denied it just one–the state’s most recent request to regulate greenhouse gas emissions from motor vehicles.
