Opening arguments in a challenge to the Defense of Marriage Act (DOMA) began Thursday before a federal judge in Boston, the AP reported.

The Boston-based gay rights group Gay & Lesbian Advocates & Defenders (GLAD), the gay rights advocacy group at the center of the gay marriage debate in New England, is representing seven gay married couples and three surviving spouses from Massachusetts who have been denied federal benefits because of the 1996 law that defines marriage as a heterosexual union for federal agencies.

GLAD lawyer Mary L. Bonauto called the law an unconstitutional intrusion on a matter previously left to states.

“All the federal government has ever cared about is that the person is married at the state level,” she argued before US District Court Judge Joseph L. Tauro. “For the first time ever, DOMA departed from that.”

Bonauto asked Tauro to rule in the group's favor without a trial.

Lawyers representing the government said that while the Obama Administration supports repeal of the law, the Department of Justice has a responsibility to defend the laws enacted by Congress, and asked for the suit to be dismissed.

“This presidential administration disagrees with DOMA as a matter of policy,” W. Scott Simpson, a DOJ lawyer argued. “But that does not affect its constitutionality.”

Speaking to reporters after oral arguments, Bonauto said: “The judge was clearly prepared. He asked good questions of both sides. And I think he completely understands this case.”

If a trial is ordered, it would be the second at a federal level concerning gay and lesbian couples' right to marry.

The first such trial is expected to wrap up in June after a federal judge heard more than three week's worth of testimony in January. Lawyers representing a gay and a lesbian couple argued that California's gay marriage ban, Proposition 8, violates their constitutional rights.

GLAD's case focuses narrowly on federal benefits being denied to legally married couples in Massachusetts, the first state to legalize the institution in 2004.

One plaintiff, Dean Hara, the widower of former U.S. Rep. Gerry Studds, the first openly gay member of Congress, has been denied the Congressman's pension and other benefits extended to surviving spouses.

“It hurts,” said Hara, who married Studds in May 2004. “But at the same time I realize that I, as a man, need to stand up for what I believe in. This is a nation of laws, and we're all supposed to have equal treatment under the law.”

Both lawsuits are expected to reach the Supreme Court.