The Justice Department will now take the position in court that the act should be struck down as a violation of same-sex couples' rights to equal protection under the law, the New York Times reports today. 

Attorney General Eric H Holder Jr sent a letter to Congress on Wednesday that says both he and the president have decided that classifications based on sexual orientation "warrant heightened scrutiny and that, as applied to same-sex couples legal married under state law", an important provision of the act is unconstitutional. 

Legal scholars in the US said the government's new position could have implications for the rights of gays and lesbians that extend beyond the Marriage Act. 

The NY Times quotes Tobias B. Wolff, a law professor at the University of Pennsylvania, who advised the Obama campaign not he gay rights issues, who said: "It's a monumentally important decision."

“The Justice Department and the president have taken the position on behalf of the United States government that discrimination against gay and lesbian people in all cases is presumptively unconstitutional,” he told The NY Times. 

This is the first time the United States government has ever embraced that position. Wolff said that if the courts agree, "it will help to eradicate all of the various forms of discrimination that gay and lesbian people suffer around the country".

The president has long opposed the Defense of Marriage Act, and has instead favoured civil unions over gay marriage.