Re:So... Why not? (Score 1)

There are several places in the Clean Air Act like this. The reason is because back when the CAA was being drafted, California was already tackling air pollution problems (due to nasty smog in L.A.) with its own laws. Rather than override what California had already done, the CAA adopted a split strategy. Under the CAA, California has the right to set its own air pollution related regulations that are stricter than those in the CAA. Other states then have the option of adopting either the California version or the general U.S. version. Many northeastern states have adopted California's regs. Car manufacturers (and business interests in general) were very concerned that there would be different requirements in every state, and this split was a compromise. Incidentally, now that the Supreme Court has asserted that greenhouse gases are indeed pollutants that can and should be regulated under the CAA, California is developing regulations to curb CO2. Northeastern states are expected to follow suit. Disclaimer: I'm not a lawyer, but an air quality researcher.