The U.S Supreme Court on Friday agreed to hear two gay marriage cases, including one in which federal benefits for a Massachusetts couple were denied under the Defense of Marriage Act, and another that overturned California's Proposition 8, which defined marriage as a union between a man and a woman.

The court said it will hear oral arguments in late March. 

The case that has attracted the most attention from advocates and opponents alike is Windsor v. United States. The plaintiff, Edith Windsor, was required to pay a significant federal tax on the estate that she had inherited from her partner, who died in 2009. The federal government cited the 1996 Defense of Marriage Act, which prevents the federal government from recognizing gay marriage and forbids the provisioning of tax benefits and other inducements offered to married men and women. 

In both cases, the court seems to be giving itself a lot of leeway; it accepted the petitions to hear the cases in a way that would allow it to rule either broadly, overturning or affirming the decisions on constitutional grounds, or narrowly, which would mean that the court's decisions would not significantly change the legal landscape for gay marriage.

Court watchers I've corresponded with believe that the likeliest outcome, given the justices' individual histories on similar questions, would be a decision that strikes down the federal recognition prong of DOMA while also ruling there is no constitutional right to get married. This result would mean that married gay couples would be eligible for federal benefits but that gays could only get married in states where such unions were legal.

In theory, a gay couple would be able to marry in a state that allowed gay marriage and then return to their home state, receiving federal benefits but no state recognition. It is difficult to predict because the court could do a lot of different things.

There is significant momentum in a number of states to legalize gay marriage by referendum or law; some gay rights advocates say that, as painful as it might be for gays living in states that won't legalize marriage for awhile, the state-by-state process confers significant legitimacy on their unions in a way that a court-imposed fiat might unleash backlash.

What can be said about how the court will rule is this: There is no way to build a majority coalition against gay rights in general because Justice Anthony Kennedy has become an impassioned advocate for gay rights; assuming he votes with the court's liberals, there are at least five reliable ideological supporters of the advance of gay rights. Chief Justice John Roberts is a cipher on the issue.  

Arguing in favor of gay rights will be the U.S. Solicitor General, Don Verrilli.  

Paul Clements, a solicitor general under President George W. Bush, will argue against them.