LGBT rights supporters are heralding a recently filed legal brief against the Defense of Marriage Act — the first of its kind against the anti-gay law from the Obama administration — as a landmark document that will aid in bringing about the end of DOMA.

Filed on July 1 by the Justice Department, the 31-page brief argues that Section 3 of DOMA, which prohibits federal recognition of same-sex marriage, is unconstitutional because laws related to sexual orientation under precedent of the U.S. Supreme Court should be subject to heightened scrutiny, or must be shown to advance a significant government interest to stay on the books.

“Section 3 of the Defense of Marriage Act … unconstitutionally discriminates,” the brief states. “It treats married same-sex couples who are legally married under their states’ laws differently than similarly situated opposite-sex couples, denying them the status, recognition and significant federal benefits otherwise available to married persons.”

The Justice Department contends LGBT people are a suspect class, or a group likely subject to differential treatment, because they’ve been subject to a history of discrimination, they exhibit immutable characteristics, and they’re minorities with limited political power. Additionally, the brief contends sexual orientation bears no relation to a person’s ability to contribute to society.

The brief argues that Congress enacted DOMA in 1996 out of motivation “in substantial part by animus toward gay and lesbian individuals and their intimate relationships” and states Congress advanced no other material interest in passing the law.

Joe Solmonese, president of the Human Rights Campaign, said in a statement that the brief represents “a watershed moment” in the LGBT rights movement.

“Now the federal government has taken that historic stand a step further and put real meat on the bones of why there is no basis for DOMA to stand,” Solmonese said. “This step represents real leadership from the Obama administration and further hastens the day in which we will leave this odious law in the dustbin of history.”

Notably, the brief recalls the U.S. government’s role in discriminating against LGBT people in its description of the ways in which LGBT people have received different treatment over the course of history. The Justice Department recalls that former President Eisenhower signed an executive order adding “sexual perversion” as grounds for dismissal for federal employees.

“The federal government enforced Executive Order 10450 zealously, engaging various agencies in intrusive investigatory techniques to purge gays and lesbians from the civilian workforce,” the brief states. “The State Department, for example, charged ‘”skilled” investigators’ with ‘interrogating every potential male applicant to discover if they had any effeminate tendencies or mannerisms,’ used polygraphs on individuals accused of homosexuality who denied it, and sent inspectors to ‘every embassy, consulate and mission’ to uncover homosexuality.'”

The brief was filed in the case of Golinski v. U.S. Office of Personnel Management. Plaintiff Karen Golinski, a lesbian federal court employee, sought medical coverage for her spouse, but the U.S. government denied this coverage because of DOMA. The Justice Department asks the federal court not to dismiss this claim.

Tara Borelli, a Lambda Legal staff attorney who’s representing Golinski in the litigation, said the “very forthright way” that the brief looks at the history of discrimination against LGBT people from the U.S. government — as well as state and local governments — is particularly striking.

“It is a very honest look at the painful way that the government has discriminated against gay people and the toll that’s taken on our community,” Borelli said.

The Justice Department also responds to an earlier brief that the House, which was filed in defense of the law under the direction of Speaker John Boehner (R-Ohio). The brief was written by private attorney Paul Clement, whom Boehner hired to litigate on behalf of DOMA in the lawsuits against the anti-gay law.

At one point, the brief disputes the House’s claim that marriage should be left between one man and one woman because that union is the best situation for child-rearing.

“There is no sound basis for concluding that same-sex couples who have committed to marriages recognized by state law are anything other than fully capable of responsible parenting and child-rearing,” the brief states. “To the contrary, many leading medical, psychological and social welfare organizations have issued policies opposing restrictions on lesbian and gay parenting based on their conclusions, supported by numerous studies, that children raised by gay and parents are as likely to be well-adjusted as children raised by heterosexual parents.”

John Aravosis, the gay editor of AMERICAblog who drew attention to the anti-gay rhetoric in the first brief in supporting DOMA that came out of the Obama administration in 2009, said the language in the most recent Justice Department brief “looked pretty amazing.” Still, he criticized the administration for filing it late on a Friday night before a holiday weekend.

“Why didn’t the president announce the existence of this brief two days earlier when meeting with the community’s leaders in the White House to celebrate the Stonewall anniversary?” Aravosis said. “The brief appears to be quite historic, so why attempt to hide it? It’s hard not to conclude that this brief was intentionally buried by the administration in order to minimize mainstream media coverage.”

The Obama administration notified plaintiffs in a document June 3 that it intended to file a brief against DOMA in the Golinski case. Tracy Schmaler, a Justice Department spokesperson, said the decision to litigate against DOMA is consistent with U.S. Attorney General Eric Holder’s announcement on Feb. 23 that the Obama administration determined that the anti-gay law is unconstitutional.

Doug NeJaime, a gay law professor at Loyola Law School, said the Golinski brief marks the “fullest elaboration of the administration’s new position” on DOMA that Holder announced to Congress in a February letter.

“We had the Holder letter and now we have a whole brief sort of spitting out the arguments that Attorney General Holder made in that letter,” NeJaime said. “It’s a really substantial brief explaining why sexual orientation should get heightened equal protection, and it fits all of the main arguments that gay rights lawyers have been hitting and that are necessary for the court to find that there’s what the administration argues are a quasi-suspect classification.”

NeJaime added he expects similar briefs in other pending lawsuits challenging the constitutionality of DOMA: Gill v. OPM, Commonwealth of Massachusetts v. Department of Health & Human Services, Pedersen v. OPM and Windsor v. United States.

Observers say the Justice Department’s decision to take an active role in attacking DOMA in these lawsuits would make the courts more apt to declare the law unconstitutional.

Borelli said the brief from the Justice Department should prompt the courts to “look with even deeper suspicion” at DOMA.

“It should help hasten DOMA’s demise because it’s very powerful that the federal government admits that gay discrimination under the law is simply not suitable,” she said.

Similarly, NeJaime said the brief from the Obama administration gives the argument against the anti-gay law “a more objective and non-advocacy type flavor.”

“It’s not just the adversarial parties before the court, it’s actually the government now saying this is the proper way to analyze this, so I think it carries a lot of weight,” NeJaime said.

But whether the administration’s brief would mean a quicker end to DOMA remains in question. Advocates previously said they expect DOMA litigation to come to the Supreme Court in 2013.

NeJaime added the Obama administration’s position on DOMA may in fact mean the process for striking down DOMA could take longer.

“If anything it may have the effect of delaying the litigation because now we have the House involved as well, and so it actually makes the litigation a little more complicated, but I do think it’s something that favors the courts striking down and eventually getting this up to the Supreme Court,” NeJaime said.