I'm so tempted to offer a wager on that. I think it'll be struck down on the narrow basis of equal protection
I'd take that bet, in a heartbeat. First of all, it's exceptionally unlikely that if certified, it wouldn't be overturned. Unfortunately, California has the ludicrous direct democracy initiative laws I'm sure you're familiar with, so for Scotus to affirm they have to find space for ignoring the stare decisis of that process, and repeal of the state's constitutional amendment based on a federal constitutional argument.
The one you propose would almost have to call DOMA in question and open the floodgates for cases in every state, and we'd have circuits ruling differently and sCOTUS being forced to look at it again, etc.
They're well aware of all of that. If they certify, it'll be to overturn. If they're sympathetic, they'll decline to review it. I'd say given the current makeup of they court, it's 65/35 they'll certify.
New law's rarely made in predictable fashion though, so who knows. Maybe Roberts is ready to make a statement we don't expect.
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