According to this Washington Post article, Obama and Holder intend to nullify the Defense of Marriage Act.
In an extraordinary change, Attorney General Eric H. Holder Jr. said Wednesday that he and President Obama had determined – after an extensive review – that the law’s key section is unconstitutional. “Given that conclusion, the President has instructed the Department not to defend the statute” in court, Holder said in a statement.
The word nullification is not used but that is exactly what Obama and Holder have done. Put aside for the moment whether or not you favor or don’t favor the Defense of Marriage Act. Obama and Holder have both the right and the obligation to nullify a law if they determine that the law is not constitutional. States have exactly the same right and obligation ( see my earlier post on nullification). This I think this is a good precedent.