"Informing the courts of the administration's view that a law is unconstitutional, while facilitating the participation of amicus who will argue in defense of the law, is respectful of the role of the other branches, both Congress and the judiciary," said law professor and former Clinton administration Solicitor General Walter Dellinger.
Brian Brown, president of the National Organization for Marriage, said he believes Republican lawmakers are preparing to intervene.
"We've been in a lot of discussions with leadership with members of Congress and look, they're looking at the case, they're making decisions as we speak. And I expect them to step in and defend the law," he said on ABC News' "Top Line."
Regardless of who stands in to legally defend DOMA, legal experts point out, a federal court -- likely the Supreme Court -- will ultimately decide whether DOMA is constitutional.