Due to its vehicle regulations that preceded the federal Clean Air Act (CAA) of 1970 and its particularly severe motor vehicle-related air quality air issues, the state of California retains the unique authority as a U.S. state to set emission standards. As a result, under federal law, any California vehicle emissions standards must meet or exceed federal emission regulations. Under the Federal Air Quality Act and Section 209 of the CAA, the State of California is required to request, and be granted a waiver from the US Environmental Protection Agency (EPA) Administrator in order to implement any proposed standards. Under this provision, the California Air Resources Board (CARB) has requested and received over 50 waivers.
Although States besides California are not permitted to develop their own emissions standards, Section 177 of the Clean Air Act authorizes other States to choose to adopt California’s standards in lieu of federal requirements. States are not required to seek EPA approval before adopting California’s standards. There are 12 such “Section 177 States.”