Off the bench, Chief Justice John Roberts Jr. can be disarmingly modest about the role of the chief justice. He is only one of nine justices, he’ll say in public appearances, and he has no authority to tell his eight colleagues what to do — even though he gets blamed when things go wrong. On Tuesday, that self-deprecating posture was on display on the bench during a brief, surprising exchange at oral argument.

It came during argument in Hertz Corp. v. Friend, an important business case on how to define a corporation’s principal place of business for purposes of federal diversity jurisdiction. The debate focused on the various ways federal appeals courts have answered that question. As we reported here, the justices seemed to be leaning toward a simple test of where a company’s headquarters or “nerve center” is located — a test advocated by Sri Srinivasan of O’Melveny & Myers, the lawyer for Hertz.