Richard, I read an article the other day that stated that the Clean Air Act of 1970 specifically gave California the right to regulate auto emissions within California. I can't remember if any other details were offered, but this might explain why they have to get approval from the feds before they can implement regs that are more strict than the federal regs - they are required to get permission via the CAA of 1970. Also, IIRC, over the years their requests were approved every single time until the most recent refusal during the Bush administration, which of course has now been resolved with this week's announcement.
Personally, I'd like to see the government place a "special" gas tax on California related to its more stringent regs, if they choose to enact them after 2016. Raise the price of gas to, say $8.00/gallon, and I don't think any of the manufacturers will have a problem selling the type of product mix the politicians seem to want. Of course, the politicians will never grow a set large enough to actually confront their constituency with the reality of things - that's why California is in such a mess today.