I used to be very much against this kind of governance, but after living in California for the past several years I see the necessity of it. See, CA has to suffer some of the worst pollution in the country. I say "suffer" because the vast majority of the air pollution is a direct result of the twin ports of Los Angeles and Long Beach--the ships that until recently idled, the idling filthy diesel trucks that receive the imported goods, the belching diesel locomotives that ship the goods across the country...to where? Oh yeah, all 47 other contiguous states.
California has come so far since the 1970s when smog was so bad you couldn't even see downtown from a mile away, or the tops of skyscrapers when you were right next to them on the Harbor Freeway. That said, there's a lot more improvements to air quality that need to be made, and also a social justice aspect as well--poor people who can only afford to live next to the freeway shouldn't have to be plagued with noxious air. Their children shouldn't come inside from playing in the backyard covered in diesel soot. Hell, you can't even park your car outside for an hour without it being covered in filth.
It's for reasons such as these that the current standards are not strict enough for many states. If California wants to regulate its emmissions with tougher standards, then I have no problem with it because of all the good that will come out of it. The fact that 14 other states want to join on, though, speaks volumes to me of how what I have seen and observed out here more than likely is mirrored across the U.S.