Massachusetts Attorney General Martha Coakley says the federal Defense of Marriage Act (DOMA) is unconstitutional in a challenge to the law, the AP reported.

The lawsuit filed in July by Coakley on behalf of the 15,000 gay and lesbian couples that have legally wed in Massachusetts since the state legalized gay nuptials in 2004 challenges section 3 of DOMA, which defines marriage as a heterosexual union for federal agencies.

In papers filed Thursday, Coakley asked a judge to declare the law unconstitutional without holding a trial on the lawsuit, saying the law interferes with her state's right to regulate marriage.

“Throughout our history, marital status has been determined solely and exclusively by State law – not simply for purposes of State legislation, but also wherever Congress has chosen to make federal law turn on marital status,” Coakley said.

“The federal government has no legitimate interest in 'preserving the status quo' where the status quo is invidious discrimination,” she added.

Massachusetts became the first state to legalize gay marriage in 2004. Since then, 4 out of 6 New England states have followed suit.

Coakley's lawsuit is one of several challenging the federal government on the issue of gay marriage. A second lawsuit filed by the Boston-based gay rights group GLAD also calls portions of DOMA unconstitutional. And the first federal trial to consider the constitutionality of Proposition 8, California's gay marriage ban, concluded last month in a San Francisco courtroom and a ruling is expected in March. The cases could reach the Supreme Court.

Coakley also argues that the federal law forces Massachusetts to discriminate against married gay couples.

“Massachusetts cannot receive or retain federal funds if it gives same-sex and different-sex spouses equal treatment, namely by authorizing the burial of a same-sex spouse in a federally-funded veterans' cemetery and by recognizing the marriages of same-sex spouses in assessing eligibility for Medicaid health benefits,” she said.