I'm seeing some contradicting coverage on this. But it seems from this account that the Obama administration has concluded that one part of the Defense of Marriage Act, which defines marriages as only between a man and woman, is unconstitutional. The administration has instructed the Justice Department not to enforce it, certainly as far as legally married couples are concerned.
Does this mean the administration refuses all defenses of the act in any form and Congress will have to step in? It's still confusing to me. Though that's seeming more like what's been indicated. More analysis here.