Did anyone challenge the CA emission laws at the US Supreme Court? Seems to me that "emissions" are not confined to state borders. Besides, it impedes trans-state commerce.
I wouldn't count my chickens on that. When I drove a CA-plated Mazda 3 from Hertz one-way SEA to SAN last June, I was amazed to see permanent-looking tollbooth-style signs announcing a checkpoint ahead. This was on I-5 southbound soon after the CA border with OR. Sure enough, the lanes converged at several stop signs. The police officer said they're looking for pest-infested fruit. Goodness. This is a state that seems to think it's a different country.