During the February 2011 oral argument in Bond v. United States, Supreme Court Justice Anthony Kennedy chided one of the lawyers standing before him for giving too little respect to the principles of federalism. The case arose from a criminal defendant's 10th Amendment challenge to a federal charge. "Your underlying premise," Kennedy complained, "is that the individual has no interest in whether or not the State has surrendered its powers to the federal government, and I just don't think the Constitution was framed on that theory."

Several months later, in his majority opinion in the case, Kennedy expounded further on the connections between federalism and individual liberty. "The federal system rests on what might at first seem a counterintuitive insight, that 'freedom is enhanced by the creation of two governments, not one,'" Kennedy wrote. "The Framers concluded that allocation of powers between the National Government and the States enhances freedom, first by protecting the integrity of the governments themselves, and second by protecting the people, from whom all governmental powers are derived."

Next week the Supreme Court will get an opportunity to test Kennedy's ideas on federalism and liberty when it hears oral argument in United States v. Windsor, the case arising from the legal challenge to the 1996 Defense of Marriage Act (DOMA). At issue is whether Section 3 of DOMA, which forbids the federal government from recognizing same-sex unions that are permitted under state law, violates the equal protection component of the Fifth Amendment.

The Obama administration, which previously defended DOMA in court, now favors the law's destruction. "Section 3 of DOMA targets the many gay and lesbian people legally married under state law for a harsh form of discrimination that bears no relation to their ability to contribute to society," the government's brief states. "It is abundantly clear that this discrimination does not substantially advance an interest in protecting marriage, or any other important interest."

That argument is likely to resonate on the Court, especially among the liberal justices. But Windsor is not just an equal protection case; it's a federalism one as well. That point was driven home earlier this month when a group of prominent constitutional scholars, including Ernest Young of Duke Law School and Randy Barnett of the Georgetown Law Center, submitted a powerful friend of the court brief attacking DOMA for exceeding the proper limits of federal power and trampling on legitimate state authority. "States derive the power to define marriage from their police powers, but Congress has no such power," the brief holds. "Nor can Congress justify DOMA under the Commerce, Spending, or Necessary and Proper Clauses." In short, "Congress has no legitimate interest in defining marriage because it lacks enumerated power to do so."

If that sounds like the sort of argument the Supreme Court's conservative members often make, it's because they do. The federalism brief is tailor-made to appeal to right-leaning advocates of federalism. As a result, it's very likely to influence Kennedy. But what about the other conservatives? Will it draw their support in this hot-button case?

Chief Justice John Roberts may at first seem like a possibility, especially in light of his aisle-crossing performance last year in National Federation of Independent Business v. Sebelius, where he sided with the liberals to uphold the Patient Protection and Affordable Care Act. But in that case, Roberts voted to affirm federal power, a common theme in his jurisprudence. Indeed, if you review Roberts' record, you'll find not only broad support for federal authority, such as his 2010 vote to give federal officials wide power under the Necessary and Proper Clause, you'll also find repeated statements urging judicial deference to Congress. In his health care ruling, for instance, Roberts declared, "It is not our job to protect the people from the consequences of their political choices." It's not difficult to imagine the chief justice striking a similar pose while upholding the Defense of Marriage Act.

Justice Clarence Thomas, on the other hand, may prove more receptive to the federalist case against DOMA. Thomas' record includes strong arguments in support of state over federal power on issues as different as medical marijuana, consumer safety laws, and the sale of body armor to felons. Nor has Thomas had any problems breaking with his usual conservative allies in a case where his federalism principles might lead him to reach a "liberal" result.

Between the equal protection challenge on the one side and the federalism challenge on the other, the Defense of Marriage Act stands on shaky constitutional ground. If either Kennedy or Thomas (or both) accept one of those arguments against the law, DOMA's days are numbered.