Arizona v. New Mexico

In Arizona v. New Mexico, 425 U. S. 794, 796 (1976), the Supreme Court declined to exercise original jurisdiction of an action by Arizona against New Mexico challenging a New Mexico electricity tax because of a pending state-court action by three Arizona utilities challenging the same tax: "We are persuaded that the pending state-court action provides an appropriate forum in which the issues tendered here may be litigated." (425 U. S., at 797.)