The Obama administration isn't challenging the ruling -- the president has said he supports same-sex marriage. Lawyers representing House Republicans are taking up the case, since both Windsor and the administration are taking the same legal position.
[Updated at 7:58 a.m. ET]
Just a few minutes until the doors open to the Supreme Court.
[Updated at 7:22 a.m. ET]
While yesterday dealt with big questions (Who should be allowed to marry? What is the impact of same-sex marriage on children?), today's arguments will look at a relatively clearer issue -- discrimination, according to CNN's senior legal analyst Jeffrey Toobin.
The arguments over DOMA will focus on the nine states plus the District of Columbia, which allow same-sex marriage. Will they treat same-sex couple the same as straight couples?
"It's a case about money, benefits and who can be denied those benefits," Toobin said.
[Posted at 7:06 a.m ET.]
We're gearing up this morning for round two of oral arguments at the Supreme Court over same-sex marriage.
Yesterday, the justices heard both sides of California's Proposition 8. The overriding legal question in that case is whether the Constitution's guarantee of equal protection under the law prevents states from defining marriage as that state has done. Some 80 minutes of arguments left no clear picture of how things might go -- but here's what we learned from it.
Today's arguments deal with the 1996 Defense of Marriage Act, which like Proposition 8, defines marriage as only between a man and a woman. The federal law means federal tax, Social Security, pension, and bankruptcy benefits, and family medical leave protections do not apply to gay and lesbian couples.
Arguments are scheduled to start at 10 a.m. ET. We'll have all the latest developments here.