The court, in a 5-4 vote, said Wednesday DOMA violated the equal protection guarantee of the Fifth Amendment.
The ruling does not recognize a federal right to same-sex marriage. Instead, it reaffirms the right of states to approve same-sex marriage without federal interference, and opens up an array of federal benefits and considerations that had been denied to same-sex couples who had been legally married in states that allow such marriages.
Since the Obama administration refused to defend DOMA at the Supreme Court, lawyers for the Republican House leadership, including Boehner, stepped in to do so.
"Congress passed the Defense of Marriage Act on an overwhelmingly bipartisan basis and President Clinton signed it into law" in 1996, Boehner said in a statement. "The House intervened in this case because the constitutionality of a law should be judged by the [Supreme] Court, not by the president unilaterally. While I am obviously disappointed in the ruling, it is always critical that we protect our system of checks and balances. A robust national debate over marriage will continue in the public square, and it is my hope that states will define marriage as the union between one man and one woman."
The Alliance Defending Freedom, a Christian non-profit, also expressed disappointment.
"The Supreme Court got it wrong in saying that a state that has redefined marriage can force that definition on the federal government," the group's senior counsel Austin Nimocks said. "The federal government should be able to define what marriage is for federal law just as states need to be able to define what marriage is for state law. Americans should be able to continue advancing the truth about marriage between a man and a woman and why it matters for children, civil society, and limited government.
"Marriage -- the union of husband and wife -- is timeless, universal, and special, particularly because children need a mother and a father. That's why 38 states and 94 percent of countries worldwide affirm marriage as the union of a man and a woman."
Obama praised the ruling, calling DOMA "discrimination enshrined in law."
"I applaud the Supreme Court's decision to strike down the Defense of Marriage Act," Obama said in a statement from the White House. "This was discrimination enshrined in law. It treated loving, committed gay and lesbian couples as a separate and lesser class of people. The Supreme Court has righted that wrong, and our country is better off for it. We are a people who declared that we are all created equal -- and the love we commit to one another must be equal as well.
"This ruling is a victory for couples who have long fought for equal treatment under the law; for children whose parents' marriages will now be recognized, rightly, as legitimate; for families that, at long last, will get the respect and protection they deserve; and for friends and supporters who have wanted nothing more than to see their loved ones treated fairly and have worked hard to persuade their nation to change for the better."
Edie Schlain Windsor, who legally married Thea Spyer in Canada, was the DOMA challenger. After Spyer died, Windsor was ordered to pay estate taxes that would not have been levied on a the survivor of a heterosexual marriage.
The American Civil Liberties Union released a statement from her after the ruling.
"DOMA violated the fundamentally American principles of fairness and equality," Windsor said. "Because of today's Supreme Court ruling, every child born today will be able to grow up in a world without DOMA -- a world where the federal government won't discriminate against their marriages no matter who they are. I know Thea would have been so happy and proud to see how far we have come in our fight to ensure that all gay and lesbian couples are treated with the dignity and respect that they deserve."
"This is truly a day for the history books, one that will be marked by future generations as a giant step forward along our nation's continuing path towards equality," said Roberta Kaplan of Paul, Weiss, who argued Windsor's case at the Supreme Court. "DOMA was the last law on the books that mandated discrimination against gay people by the federal government simply because they are gay. The days of 'skim milk' or second-class marriages for gay people are now over."