The California Supreme court just overturned the state's ban on gay marriage for being discriminatory and unconstitutional. Okay, and like, Republican appointees outnumber Democrat appointees on the court 6 to 1. "Scholars have described the court under the leadership of Chief Justice Ronald M. George as cautious and moderately conservative." Um, just what we would expect from strict interpretors of the constitution! [LA Times]
@NefariousNewt: Under the Defense of Marriage Act (yuck), states are not obliged to recognize same sex marriages performed in other states (it's an open question whether DOMA is, itself, constitutional; the Supreme Court has so for refused to hear cases challenging it).
In any event, other states would not have standing to challenge California's interpretation of its own constitution. What is more likely to happen is that other states would refuse to recognize the marriages, and you would have individuals going to court to force those states to do so on the basis that the refusal violates the full faith and credit clause. Eventually, the Supreme Court may hear one of those cases but, regardless of its decision, same sex marriage would still be legal in California.