DOMA is currently the law, and the executive branch should uphold it. If they want to change it, then Obama should have his compatriots in congress introduce a bill to repeal or change it.
Now, having said that, I couldn't give a tinker's damn if homosexuals wish to marry. It does not affect my marriage in the least. And anyone who says that it affects them, unless they are gay, is full of it.
Well you're one person with one opinion. Thank God the vast majority DO care what marriage is, and want to keep it that way without being defiled by a bunch of perverts.