So what's Arnie gonna do now? This is bad timing for him. He can further alienate his Republican base by letting it become law - not good in an election year. Or he can veto it and alienate the social liberals that he's been pandering to. Decisions, decisions!
Arnie won't even sniff a veto on this. I'm pretty sure he would sponsor it if he could. Do hetero married couples in CA have the same option to file as either joint or separate?