Days before the 2008 election, then-candidate Barack Obama said California’s Proposition 8 was “unnecessary” and “not what America’s about.”

Now, some same-sex marriage advocates are hoping Obama’s Justice Department will make a similar argument in court.The federal government is not a party to the Proposition 8 litigation, which pits gay and lesbian couples against supporters of a state constitutional amendment banning same-sex marriage. But the Justice Department could weigh in as amicus curiae — either when the case arrives at the steps of the U.S. Supreme Court or, sooner, before the U.S. Court of Appeals for the 9th Circuit. Such a decision would typically be up to Acting Solicitor General Neal Katyal with input from across the federal government, including the White House.

The involvement of the Justice Department would add further significance to what is already the nation’s most-watched court case, officially named Perry v. Schwarzenegger, while also raising difficult political questions for the Obama administration. “There have been people encouraging the U.S. Justice Department to follow the progress of the Perry case, to discuss it internally and to support the civil rights of gay and lesbian Americans,” said Jennifer Pizer, director of Lambda Legal’s Marriage Project, which filed an amicus brief in the case’s trial phase.

Pizer would not detail internal strategy, such as lobbying of White House or Justice Department officials, but she and other advocates of same-sex marriage said there are reasons for the federal government to become involved in the case. For one, there are Obama’s 2008 commentsin opposition of Proposition 8. For another, they argue, the federal government has an interest in protecting civil rights — though that interest has been complicated in the context of homosexuality.

Or Pizer said, there’s yet another argument advocates could use to persuade DOJ to become involved: The administration could side-step the marriage question and take a position instead on whether Proposition 8 proponents have standing to appeal. If the appeals court finds they do have it, “the implications of that may well be to invite lots of contentious litigation” because, she said, it would mean someone could litigate in federal court “due simply to having opinions about someone else’s rights.”

Obama, however, has staked out a complicated position on same-sex marriage. He has said he continues to oppose the idea, even while he denounced Proposition 8, and that view has not escaped the notice of Charles Cooper of Washington’s Cooper & Kirk, who is leading the defense of Proposition 8. In a filing with the 9th Circuit, Cooper wrote that the trial court’s invalidation of Proposition 8 “defames” people who oppose same-sex marriage, including “the current President of the United States.” In an interview, Cooper said he has not had any contact with DOJ about the case.

Justice Department spokeswoman Tracy Schmaler declined to comment.

It is possible that the 9th Circuit panel could request the Justice Department’s views on the case, but Carter Phillips, managing partner of Sidley Austin’s Washington office, said it would be unusual for a panel to do so. The Justice Department would become involved, he said, only after the Solicitor General’s Office feels pressure to do so — either from below, among litigants, or from above, among officials at the White House.

“Somebody would have to get the SG energized to weigh in,” said Phillips, who served as an assistant to the solicitor general during the Reagan administration. “The SG has never viewed himself or herself as having a roving interest to go around and find cases that he or she has an interest in.”

Potentially complicating the department’s situation is its defense of the federal Defense of Marriage Act in U.S. District Court in Massachusetts. The 1996 law limits federal benefits for same-sex couples and, though Obama says the law is discriminatory, Justice Department lawyers defended its constitutionality by saying it could be “rationally related to legitimate governmental interests.”

The ruling against Proposition 8 by U.S. District Chief Judge Vaughn Walker of the Northern District of California criticized similar arguments.

Christopher Stoll, a senior staff attorney at the National Center for Lesbian Rights, said the Justice Department need not take a position on same-sex marriage in order to oppose Proposition 8. He cited the U.S. Supreme Court’s 1996 ruling in Romer v. Evans, striking down a Colorado state constitutional amendment for treating gays and lesbians as an inferior class. “There’s a way of looking at Proposition 8 that could require its invalidation under the equal protection clause without getting into other issues,” Stoll said.

David Ingram can be contacted at