The historic decision by the 2nd circuit US court of appeals in Manhattan stems from activist Edith Windsor's fight to have her marriage to Thea Spyer in New York, recognised by the US government.
"I am thrilled. I look forward to the day when the federal government recognises the marriages of all Americans. Marriage is a word that has magic. There is a legitimacy to it that makes it important," the New York Daily News quoted Windsor, as saying.
According to the report, Windsor married her partner of 44 years in Canada in 2007 and New York recognised the couple as married even before the state legalised gay marriage in 2011.
However, when Spyer died in 2009, Windsor had to pay 353,000 dollars in federal estate taxes, the same taxes a stranger would have paid on the inheritance, and unlike married heterosexual couples who are exempted from the procedure.
It was because the US government did not recognise Windsor's union due to the 1996 Defense of Marriage Act, which defines marriage as 'between a man and a woman', the report said.
The ruling marks the second time when a federal appeals court declared the Defense of Marriage Act unconstitutional. Earlier this year, the circuit court covering Massachusetts rejected the law, it added.