The statute had been challenged by Edith "Edie" Windsor, who sued the government for failing to recognize her marriage to her partner Thea Spyer, after Spyer’s death in 2009. Windsor and Spyer were married in Canada in 2007, and were considered married by their home state of New York.

"Thea and I shared our lives together for 44 years, and I miss her each and every day," said Windsor. "It’s thrilling to have a court finally recognize how unfair it is for the government to have treated us as though we were strangers."

In her lawsuit, Windsor argues that DOMA violates the equal protection guarantee of the U.S. Constitution because it requires the government to treat same-sex couples who are legally married as though they were not, in fact, married. Windsor's lawsuit was filed by the law firm of Paul, Weiss, Rifkind, Wharton & Garrison LLP, the American Civil Liberties Union.

The Obama administration declined to defend the statute in court in February, 2011, so the House of Representatives’ Bipartisan Legal Advisory Group appointed an attorney to represent the government in the case.

When Thea Spyer died in 2009, she left all of her property to Windsor, including the apartment they shared. Because they were married, Spyer's estate normally would have passed to her spouse without any estate tax. But because DOMA prevents recognition of the otherwise valid marriages of same-sex couples, Windsor had to pay more than $363,000 in federal estate taxes.

"This decision adds to what has become an avalanche of decisions that DOMA can’t survive even the lowest level of scrutiny by the courts," said James Esseks, Director of the ACLU Lesbian Gay Bisexual Transgender Project.

Human Rights Campaign President Joe Solmonese added:
"The dominoes continue to fall on DOMA with yet another federal court rightly calling it unconstitutional. All loving and committed married couples should be recognized by the federal government yet we continue to see the terrible pain DOMA inflicts on real families. The real question is when Speaker Boehner will see the writing on the wall and stop wasting taxpayer dollars defending this outrageous law and instead work to repeal it. Paul Clement’s record of zero for four speaks for itself."

The New York case comes the day after the 9th Circuit Court of Appeals denied request by anti-equality proponents for a rehearing of the prop 8 case in California.

Supporters of the 2008 ban, Proposition 8, have lost two rounds in federal court but have made clear they will appeal to the U.S. Supreme Court and hope for a favorable response from the conservative-leaning court.

The top U.S. court could agree to hear the matter in the session beginning in October, putting it on track to decide the case within a year. It could also decline to review Prop 8.

The American Foundation for Equal Rights (AFER) the group that is suing have prop 8 declared unconstitutional offered :

"This ruling marks a monumental turning point in our case for equality. AFER’s federal constitutional challenge to Proposition 8 is now entering its final stage. The Ninth Circuit Court of Appeals decided today it will not rehear our case. Now, there are only two things that could happen:

Couples start getting married again in California; or Our case for marriage equality goes to the U.S. Supreme Court." — Staff