Obama is backing the states 

There are a number of legal cases winding their way toward federal courts that address the issue of whether the equal protection clause of the Constitution guarantees gay men and women the same access to marriage rights as heterosexual men and women.

There are several challenges to the Defense of Marriage Act, which bars gay men and woman from receiving federal marriage benefits and allows states to refuse to recognize valid gay marriages. Obama’s Justice Department has declined to defend the constitutionality of DOMA.

Activists in Hollywood have challenged California’s Proposition 8 constitutional ban on gay marriage. But Obama, in endorsing gay marriage, contradictorily states the decisions on marriage should be left to the states!

This means if he were a judge, Obama would reject the arguments challenging California’s approval of Proposition 8. Obama has affirmed the right of Californians and all states to mandate that marriage is between a man and a woman in their constitutions.