Later this month, the Supreme Court will hear oral argument in United States v. Windsor, the case arising from the legal challenge to Section 3 of the Defense of Marriage Act, which forbids the federal government from recognizing same-sex unions that are lawful under state law. Last Friday, a group of legal scholars whose work focuses on federalism submitted a friend of the court brief in the case, urging the justices to invalidate Section 3 because it is not a valid exercise of federal power and therefore violates the Constitution. On Twitter, reporter Mike Sacks of The Huffington Post noted the brief and asked, “could it pick up Thomas?”

It might. Among the scholars who signed on to the brief is Georgetown law professor Randy Barnett, one of the legal architects behind last year’s Obamacare challenge and also the losing lead attorney in the 2005 medical marijuana case Gonzales v. Raich. Justice Clarence Thomas accepted Barnett’s theories on the limits to federal power in both those cases and has also cited Barnett’s work in other opinions.

But just as important, Thomas has a tendency to break with the Supreme Court’s conservative bloc when federalism principles are at stake in a case that is otherwise seen to advance a liberal political agenda—which is basically the Defense of Marriage Act controversy in a nutshell.

In 2009, for instance, Thomas concurred in the Court’s 6-3 ruling in Wyeth v. Levine, which said that federal law did not trump a state lawsuit filed against a pharmaceutical corporation, even though the drug-warning label that was at the center of the lawsuit had been approved by the Federal Drug Administration. (Chief Justice John Roberts and Justices Antonin Scalia and Samuel Alito voted in dissent.) Thomas reached a similar conclusion in another regulatory federalism case, Williamson v. Mazda Motors of America, where the Court held that federal law did not trump a more restrictive state law regulating seat belts. Thomas’ concurrence in Williamson even earned him some kudos from the left-leaning Constitutional Accountability Center, who called Thomas a “surprising ally for progressives” in the case.

Since Thomas is unlikely to ask any questions during the March 27 oral argument over the Defense of Marriage Act, we won’t know his views for certain until late June, when a decision is expected in the case.