New York Times Supreme Court correspondent Adam Liptak has an interesting article on Chief Justice John Roberts’ question about sex discrimination in yesterday’s Supreme Court oral argument in the same-sex marriage case:

In a telling moment at Tuesday’s Supreme Court arguments over same-sex marriage, Chief Justice John G. Roberts Jr. suggested that he may have found a way to cast a vote in favor of the gay and lesbian couples in the case.

“I’m not sure it’s necessary to get into sexual orientation to resolve this case,” he said. “I mean, if Sue loves Joe and Tom loves Joe, Sue can marry him and Tom can’t. And the difference is based upon their different sex. Why isn’t that a straightforward question of sexual discrimination?”

That theory had gotten only slight attention in scores of lawsuits challenging bans on same-sex marriage, and it is unlikely to serve as the central rationale if a majority of the court votes to strike down such bans, an opinion likely to be written by Justice Anthony M. Kennedy.

But it could allow Chief Justice Roberts to be part of a 6-to-3 decision, maintaining some control over the court he leads and avoiding accusations from gay rights groups that he was on the wrong side of history.

“This would be a clean, formalistic way for the court to resolve the case,” Andrew Koppelman, a law professor at Northwestern University, said in an interview. “It could just apply existing sex discrimination law.”

Professor Koppelman and other scholars filed a brief urging the court to strike down the four same-sex marriage bans before it on sex-discrimination grounds. The chief justice’s musings were similar to a passage in the brief.

Professor Koppelman and other scholars filed a brief urging the court to strike down the four same-sex marriage bans before it on sex-discrimination grounds. The chief justice’s musings were similar to a passage in the brief.

I discussed Chief Justice Roberts’ question and the exchange it prompted with other justices in this post.

As Liptak notes, the question may have been based on an amicus brief I coauthored with Andrew Koppelman, on behalf of ourselves and an ideologically diverse group of other legal scholars (though I hasten to add there is no definitive way to know whether that really is where the Chief Justice got the idea).

Liptak and others have suggested that Roberts could use the sex discrimination argument as a way to justify voting to strike down laws banning same-sex marriage without addressing the difficult issues raised by some of the other arguments at stake in the case.

As past experience shows, predicting Roberts’ positions is not an exact science. At this point, all we can say for sure is that he and at least some of the other justices are taking the sex discrimination issue seriously.

UPDATE: If Chief Justice Roberts does end up writing an opinion based on the sex discrimination issue, it is possible that Justice Ruth Bader Ginsburg (who also showed interest in the issue during the oral argument) might join him. Having litigated several of the Supreme Court’s pathbreaking sex discrimination rulings in the 1970s, Ginsburg has a longstanding interest in these issues.