District Court rulings only create precendent within that judicial district. The ruling would also bind the parties to the case (in this case the State of California) even though CA includes territory outside the Northern District of California. If the 9th Circuit actually uphelds Perry v. Schwarzenegger then the ruling will apply to the entire 9th Circuit (Alaska, Arizona, Hawai’i, Idaho, Montana, Nevada, Oregon, Washington, & Guam as well as CA). At least one of those Attorneys-General is bound to object and take it before the Supreme Court.
Now if they rule the Prop 8 sponsers don’t have standing then they never even address any of their arguments. It’s like the case was never appealed at all. And I feel confident in saying there’s zero-chance SCOTUS would overule the 9th Circuit on the issue of standing, they’re very much loath to expand the rules of standing for federal court cases. I also feel confident is saying that the Supreme Court of California isn’t going to answer the legal question certified to them in favour of Prop 8’s backers. There’s no statute in CA granting private citizens the right to defend laws in court, no legal precedent for it, and the state constitution expressly gives that duty to the Governor and the Attorney General. That same state constitution also provides 2 different mechanisms for the voters and/or the state legislature to deal with officers who do not perform their duties; neither of which has been or will be pursued in this case.