Each state and federal court might have its own inviolable power to adjudicate cases and issue orders within its territory. But that does not stop judges from cooperating in the face of mass-tort litigation that arises both in state and federal court.

U.S. District Judge Barbara Jacobs Rothstein, of the Western District of Washington and a visiting judge to the U.S. District Court for the District of Columbia, said that for many years input was not obtained from state-court judges, but that has changed.