Courts that have been established under Article III of the Constitution, including the Supreme Court of the United States, United States Courts of Appeals, and United States District Courts, are called constitutional, or Article III, courts. Article III of the United States Constitution establishes the judicial power of the federal government. The Supreme Court of the United States was created by Sec. 1 Article III of the Constitution. Its jurisdiction is set out by statute in Title 28 of the U.S. Code. Under the Constitution, the authority of the federal judiciary extends only to certain "cases" and "controversies," which are identified by either the nature of the suit or the parties involved. The Constitution establishes the Supreme Court of the United States and permits Congress to establish "inferior" federal courts. The federal judiciary currently consists of the Supreme Court, courts of appeals in 12 regional judicial circuits, two intermediate appellate courts with special power to hear cases originating nationwide, a total of 94 judicial districts throughout the 50 states that contain at least one federal district court and one bankruptcy court, territorial courts that function as district courts in several territories, and specialized tribunals that have been established by Congress pursuant to power provided in Article I of the Constitution. The district courts serve as the trial courts in the federal system, while the courts of appeals serve as intermediate appellate courts.
Under Article III of the Constitution, United States Supreme Court justices have lifetime tenure in their positions "during time of good behavior." Lifetime tenure is also true of the judges in the lower constitutional courts of the federal system. Article III of the Constitution provides that a federal court may hear a controversy between citizens of different states or citizens of the United States and citizens of foreign nations. Congress in Title 28 of the United States Code limits this power by requiring that the amount in controversy exceed $75,000. The broad purpose behind diversity jurisdiction is that a state court may show bias towards its own citizen to the detriment of the citizen from another state.