The Obama administration is asking the Supreme Court to strike down the federal law defining marriage as a union between only a man and a woman.
The request regarding the 1996 Defense of Marriage Act was made Friday in a brief by Solicitor General Donald Verrilli that argues the law is unconstitutional because it violates "the fundamental guarantee of equal protection."
The high court is set to hear two cases next month on the issue: the constitutional challenge on Proposition 8, the 2008 California that allowed same-sex marriages in the state that two years later was overturned, and United States v. Windsor, which challenges DOMA.
Edith Windsor, a California resident, was married to her female partner in Canada in 2007 but was required to pay roughly $360,000 in federal estate taxes because the marriage is not recognized under DOMA.
The law "denies to tens of thousands of same-sex couples who are legally married under state law an array of important federal benefits that are available to legally married opposite-sex couples," Verrilli’s brief in part states.
House Republicans also purportedly filed a brief Friday, arguing for the right to defend DOMA.
Obama’s move comes as no surprise, considering he said during his first term that he personally is in favor of gay marriage. And he ended the U.S. military’s “don’t ask, don’t tell” policy, opening the way for gays to serve openly.
More recently, during Obama’s second inaugural address, he hinted at further action.
"Our journey is not complete until our gay brothers and sisters are treated like anyone else under the law, for if we are truly created equal," he said.
The court is taking up the California case March 26 and has several options. Among them are upholding the state ban on gay marriage and saying residents of a state have the right to make that call.
The nine justices also could endorse an appeals court ruling that would make same-sex marriage legal in California, but it would apply only to that state.
Twenty-nine other states have constitutional amendments banning gay marriage, while nine states and Washington, D.C., recognize same-sex marriage.
Public opinion has shifted in support of gay marriage in recent years. In May 2008, Gallup found that 56 percent of Americans felt same-sex marriages should not be recognized by the law as valid. By November 2012, some 53 percent felt they should be legally recognized.
The Associated Press contributed to this report.