On June 30, 2009 the EPA granted a waiver allowing California to regulate greenhouse gas (GHG) emissions from vehicles within the state. The waiver request, which was submitted by California in 2005, had originally been denied by the EPA in March of 2008. The 2008 denial—the only full denial of a California waiver request to date –was based on the premise that the request does not satisfy the requirements for a waiver under the Clean Air Act. The EPA began reconsideration of the denial earlier this year. Under the federal Clean Air Act, California is the only state with the ability to set standards for motor vehicles, as long as these standards are as stringent as the federal standards and the state receives a waiver from the EPA. Once California receives a waiver from the federal government , other states can either adopt California standards but cannot set their own standards.
Earlier this year, President Obama announced a plan for a coordinated federal GHG standard for new motor vehicles with the same fuel economy target for 2016 (35.5 mpg) as the California standard would have achieved. California and the other states which have adopted the California standard have agreed to conform to the federal standard from 2012 to 2106. With the waiver decision, they will be able to regulate vehicle emissions from now until the federal standard takes effect in 2012, and after 2016.
EPA Notice of Decision Granting Waiver
Executive Summary of the EPA's Waiver Decision
Vehicle Greenhouse Gas Emissions Standards