That's only the case as long as complying with California's emissions laws is not too much harder than what they would otherwise have to comply with. That's a c

That's only the case as long as complying with California's emissions laws is not too much harder than what they would otherwise have to comply with. That's a complicated analysis, it's kinda got a bit of prisoner's dilemma to it. As long as companies are following CA's restrictive emissions laws, there's little incentive for other areas to make their own laws more restrictive. If companies started to ignore CA's laws (and not sold there or sold different versions) you should expect other states to start to pass more and more restrictive laws.