President Obama has told the Justice Department not to defend the anti-Constitutional, so-called Defense of Marriage Act. Specifically he has told them not to defend it in court(s), where it is obvious they would end up losing anyway based on previous judicial decisions -- the section of it disallowing the federal government from recognizing same sex marriages in states where they are performed.
In Iowa, Massachusetts, Connecticut, Vermont, New Hampshire along with a number of other states that will soon recognize it, such as in Maryland, the government turns a blind eye to the rights of states to have marriage equality for their gay citizens and residents. Just imagine a federal government in 1940 having a law that specifically does not recognize interracial marriages in Vermont because congressmen from states where such marriages are banned, pushed through legislation to ban federal recognition.
President Obama took an oath to "support and protect" the Constitution of our nation, and that includes ensuring that he does not work to defend an un-Constitutional law. The Constitution requires him that "Laws be faithfully executed" but does not require a defense of un-Constitutional or even bad laws, so he will still enforce DOMA and its sections, until struck down by a court or overturned by a future U.S. Congress.
Unfortunately, this GOP-dominated Congress won't do so. In fact, it is highly likely they will pass one pro-gay rights piece of legislation (or even allow one to come up for a vote) while they are session. The GOP is still too tied to the anti-gay Christian right-wing, except in places such as New England or maybe the Pacific Northwest.
By the way, Maryland's Senate passed marriage equality for its gay citizens, there will be a vote by their House of Delegates. Once it passes there, states such as Delaware, Rhode Island, Oregon will get marriage equality, and over the next couple of decades or so, every state in the union. It will of course, because rising support in America and among the young in every state of the union, shows that even in states such as Oklahoma, South Carolina, Alabama, that marriage equality for gay men and women, is inevitable.