BOSTON — Oral arguments in a landmark legal proceeding challenging the Defense of Marriage Act unfolded Wednesday, marking the first time an appeals court has heard a challenge to the anti-gay federal law.

Lawyers squared off over the constitutionality of DOMA, amid discussion about whether the law fails a rational basis standard of scrutiny or interferes with a state’s rights under the Tenth Amendment.

Stuart Delery, who’s gay and the Justice Department’s acting assistant attorney general for the civil division, surprised many when he said the Obama administration wouldn’t defend DOMA on any basis, including under rational basis review.

Last year, the Obama administration said it would no longer defend DOMA in court, on the basis that President Obama had determined that the anti-gay law fails heightened scrutiny because it discriminates against gay couples.

Asked by Judge Juan Torruella whether the administration has a position on the rational basis test for the law, Delery replied, “We don’t.”

Delery’s position is significant because U.S. District Judge Joseph Tauro in 2010 ruled in favor of plaintiffs on the basis that DOMA didn’t pass the rational basis standard review, or a rational means to a legitimate governmental end. Judges on the First Circuit will have to decide whether to affirm or overrule this decision.

Two cases challenging the constitutionality of DOMA are before the First Circuit: Gill v. Office of Personnel Management, filed by Gay & Lesbian Advocates & Defenders, and Commonwealth of Massachusetts v. Department of Health & Human Services, filed by Massachusetts Attorney General Martha Coakley.

The three-judge panel hearing the cases is made up of Chief Judge Sandra Lynch as well as Torruella and Judge Michael Boudin. Lynch was appointed by a Democrat, former President Bill Clinton, while Torruella was appointed by former President Ronald Reagan and Boudin was appointed by former President George H.W. Bush.

Despite the administration’s position on rational basis review stated during the hearing, Delery said heightened scrutiny, or examining the law on the assumption that it’s discriminatory toward a group of people, is the appropriate way to handle DOMA because Congress passed DOMA in 1996 out of animus toward gay people.

Delery maintained that the name “DOMA” itself indicates that the anti-gay law was intended to discriminate against LGBT families.

“It was a defense against something, and that something was same-sex couples,” Delery said.

But the administration wasn’t willing to accept all arguments against DOMA. Delery said the administration doesn’t share the view that DOMA is unconstitutional on the basis that it interferes with a state’s Tenth Amendment right to regulate marriage, saying “that’s where we disagree” with the lawsuit.

Delery said Congress has the authority to define federal programs — even those related to marriage, where states traditionally have had jurisdiction on who can and cannot marry.

Defending DOMA in court was Paul Clement, a former U.S. solicitor general. After the Obama administration declared it would no longer defend DOMA, House Speaker John Boehner hired Clement to advocate for DOMA on behalf of the Bipartisan Legal Advisory Group, which voted along party lines to take up defense of the law.

Kicking off the arguments, Clement said the Obama administration is free to change its opinion on whether DOMA would pass a rational basis test, but nonetheless the administration has previously argued in a legal brief that DOMA shouldn’t be struck down on this standard.

“It’s certainly open to the president and the attorney general to change their position, and to say that heightened scrutiny should apply, but that doesn’t make their prior submission go away, and it doesn’t make the arguments in their about why there are rational bases — in addition to some that we’ve covered in our brief — to support the statute,” Clement said.

Clement offered many reasons why DOMA should be upheld — among them was an assertion that opposite-sex marriages advance governmental interests because they can produce “unplanned offspring” unlike same-sex couples.

Additionally, Clement said DOMA isn’t an attempt to “override a state’s definition” of marriage, but merely allows the federal government to “preserve the status quo” as states began legalizing same-sex marriages in 1996 to keep benefits from federal programs, like Social Security, flowing only to opposite-sex married couples as they had in the past.

But Delery blasted the notion that procreation is a necessary component for any marriage — whether the union is opposite-sex or same-sex — saying straight couples can marry even if they don’t want and can’t have children.

“On the flip side, there are many children — hundreds of thousands, I think is the best estimate — who are being raised by same-sex parents in this country, and DOMA has the effect of denying those children the stability and protection that many of the federal benefits that we’re talking about in these cases would provide,” Delery said.

Significant discussion related to heightened scrutiny was focused on the case of Cook v. Gates, a challenge to “Don’t Ask, Don’t Tell” in which the First Circuit ruled that sexual orientation shouldn’t be considered a suspect class. Clement argued that the First Circuit is bound by this precedent not to apply heightened scrutiny to laws affecting gay people. But attorneys opposed to DOMA said this case shouldn’t be applied to the anti-gay law because courts traditionally grant the military a high level of deference.

Mary Bonauto, GLAD’s civil rights project director, represented her organization during the hearing and said the law violates equal protection under the Constitution regardless of whether heightened scrutiny or rational basis review is applied to the anti-gay law.

“To this day, the federal government defers to state marital determinations where marital status is a factor for federal protections,” Bonauto said. “But for DOMA, same-sex couples who began marrying here eight years ago like our plaintiffs would have been included in those federal laws, but DOMA’s precise point was to prevent that conclusion and created an across the board exclusion.”

Massachusetts Assistant Attorney General Maura Healey argued on behalf of Massachusetts, saying that DOMA violates the state’s right under the Tenth Amendment to regulate marriage. She said an end to DOMA would return the federal government to “what it always has done” by recognizing state authority on which couples should be able to marry.

In her conclusion, Healey drew on the lifting of “Don’t Ask, Don’t Tell” and its implications for gay troops as a reason why the court should overturn DOMA.

“I’ll take you to our state veterans cemeteries because here the operations of DOMA really revives the concept of separate but equal,” Healy said. “In this day and age, when gay people can now go serve in the military, fight for our country and even die, unlike other married service members, they can’t be buried with their spouse on state land in our veterans cemetery. Instead, Massachusetts is essentially required to build on the next hillside over a cemetery for those veterans. We think that’s wrong.”

The panel has no set time to make a ruling in the cases, but advocates are hoping for a speedy decision. Once a decision is reached, it can be appealed either to the full First Circuit or the U.S. Supreme Court.