As I understand it, the questions for the Supremes are:
(1) Do states have the right to establish their own marriage rules?
(2) Can Congress treat some marriages differently from others, as DOMA prescribes?
These are the same sort of issues that interracial couples went through. We'll see how far the Republicans have come depending on Supreme Court rulings. Observers seem to expect Kennedy to be the deciding vote, as he was when the Supremes struck down laws which the right wing of the Supreme Court defended vigorously.
Supreme Court On Gay Marriage: Prop 8, DOMA To Receive Hearings
WASHINGTON — The Supreme Court will take up California's ban on same-sex marriage, a case that could give the justices the chance to rule on whether gay Americans have the same constitutional right to marry as heterosexuals.
The justices said Friday they will review a federal appeals court ruling that struck down the state's gay marriage ban, though on narrow grounds. The San Francisco-based appeals court said the state could not take away the same-sex marriage right that had been granted by California's Supreme Court.
The court also will decide whether Congress can deprive legally married gay couples of federal benefits otherwise available to married people. A provision of the federal Defense of Marriage Act limits a range of health and pension benefits, as well as favorable tax treatment, to heterosexual couples.