After the U.S. Supreme Court heard the oral arguments for two landmark same-sex marriage cases this week, Harvard Law School professors predicted that the justices would not uphold the Defense of Marriage Act and were unlikely to make a sweeping decision concerning Proposition 8.

Lawyers argued before the court on United States v. Windsor, which addresses DOMA, the national law defining marriage as a union between a man and a woman, and Hollingsworth v. Perry, a case addressing the constitutionality of California’s ban on same-sex marriage.

In both cases, Law School professors predicted the outcomes primarily based on the questions asked by Justice Anthony M. Kennedy.

“Justice Kennedy, who everybody says is the swing vote, is usually pretty transparent about his views,” said Law School professor Mark V. Tushnet ’67. “In the DOMA case, he was very skeptical. I would be very surprised if the DOMA statute were upheld.”

Law School professor Michael J. Klarman agreed, pointing specifically to Kennedy’s response toward the debate on federal jurisdiction over the definition of marriage.

“Justice Kennedy clearly seemed to think there was a federalism problem,” Klarman said.

In the case addressing California’s Proposition 8, however, Law School professors predicted that the justices will decide the case based on its procedural integrity, not on the merit of the ban itself.

In doing so, the court would avoid setting a precedent for same-sex marriage on a state level.

“From Tuesday’s argument [regarding Proposition 8], it sure didn’t sound likely that you’re going to get a broad ruling in favor of same-sex marriage across the board,” said Klarman, who attended the oral argument as a guest of Justice Ruth Bader Ginsberg, for whom he used to clerk.

Contrastingly, Tushnet predicted that the DOMA case would be decided based on the issues of federalism and the constitutionality of same-sex marriage.

“It didn’t have the feel of a case that would be decided on procedural grounds,” Tushnet said, referencing issues raised by Law School professor Vicki C. Jackson in an amicus brief filed in January.

In her amicus brief—which was requested by the Court—Jackson argued that the justices do not have the constitutional power to issue merit-based decisions on the DOMA case.

Tushnet said he believes that Jackson’s brief on the case will not ultimately affect the justices’ decision making process.

“I would be very surprised if they accepted her arguments, and I think she would be pretty surprised too,” he said.

Ultimately, Klarman said he was cautious about making definitive predictions from the oral arguments.

“I don’t think you can be confident that you know how the justices are going to vote,” he said.

—Staff writer Dev A. Patel can be reached at devpatel@college.harvard.edu. Follow him on Twitter @dev_a_patel.