During arguments at the Supreme Court Tuesday in a water dispute that came to the Court under its “original jurisdiction” over conflicts between states, discussion of the issues led the justices into some broader questions about the nature of original jurisdiction cases and the role of special masters appointed by the Court to assist in their adjudication.

Chief Justice John Roberts Jr. seemed especially protective of the Court’s role in such matters, returning a number of times to the idea that they are a unique and important subset of the Court’s cases. At one point during the argument he expressed concern that if non-state entities are allowed to intervene in the cases, “private parties are going to hijack our original jurisdiction.”