The plaintiff, Edie Windsor, is walking out and being greeted by cheering crowds. Alicia Keys' "Girl On Fire" is blasting from speakers.
[Updated at 12:29 p.m. ET]
"The court appears to be moving toward an out, if it wants it, on procedural grounds," CNN Correspondent Joe Johns said just minutes ago. At issue is whether House Republicans have standing to defend DOMA instead of the Obama administration, which has decided not to defend it.
As for the merits of the case, there was a lot of discussion as to why the U.S. Congress passed DOMA in 1996 -- whether it was just trying to ensure legal uniformity on marriage, or whether something else was afoot, like moral disapproval of homosexuality, Johns said.
[Updated at 12:22 p.m. ET]
"They are obviously very deeply split. But I think DOMA is in trouble," says CNN Senior Legal Analyst Jeffrey Toobin after watching the arguments.
[Updated at 12:20 p.m. ET]
Both parties are leaving the courthouse right now. Stay tuned for latest developments.
[Updated at 12:16 p.m. ET]
Oral arguments on the Defense of Marriage Act at the Supreme Court have ended after nearly two hours.
[Updated at 11:49 a.m. ET]
If the high court is on schedule, the oral arguments should be more than three-quarters of the way through. Just outside, protesters are speaking out about why the fight over DOMA is so important to them.
[Updated at 11:27 a.m. ET]
A number of legal observers have pointed out that the court, when it makes its decision on DOMA later this year, could skirt the issue of same-sex marriage by simply saying that the party defending it -- the House GOP -- doesn't have the right to do so.
Jonathan Turley, a law professor at George Washington University, told CNN moments ago that this is very possible.
Congressional Republicans took up the cause after the Obama administration declined to defend the law. Turley says that judging by justices' questions in yesterday's Proposition 8 hearing, some justices are "worried about handing down a major ruling" on same-sex marriage.
"Today's case is going to be another example of that. They have an out. They can reject this case on standing, which is basically saying that one of the parties doesn't have the right to be here in court. And there are significant standing problems here, and it is right there for any justice to take as an exit," Turley said.
"... For justices that are already a little bit squeamish about this issue, they can easily take this exit and say, 'You, members of Congress, cannot speak for the nation.'"
[Updated at 11:11 a.m. ET]
Well, here's one way to look at it. CNN's Shannon Travis found a man holding a controversial sign outside the courthouse.
It says: "Good: 1 woman 1 man. Better: 1 woman 6 men. Best: 1 man 6 women."
Travis tweeted this about the sign: "Sign causes stir. Even hardcore pro/anti same-sex marriage protestors here at Supreme Court complaining about this."
[Updated at 11:02 a.m. ET]
Same sex-marriage has also divided the religious community. We've seen Catholics rallying for and against it. Barrett Duke, of the The Southern Baptist Ethics & Religious Liberty Commission, just tweeted this a little while ago:
"SCOTUS hears more same-sex marriage arguments today.Pray God gives them wisdom and understanding for His design."