As you may know, the E.P.A. denied California to set its own standards for carbon dioxide emissions from cars. One argument of the EPA is that the Federal standards were actually better. They are not. See an analysis by David Doniger:
Let’s look more closely at Johnson’s math. The EPA administrator supplied no documentation for his calculations. (My high-school son can’t get away with that when he turns in his math homework.) In contrast, the California Air Resources Board (CARB) prepared its own fully-documented comparison of the California emission standards and the federal mileage standards.