Assignment
The rules governing assignment of senior judges are also defined by statutory law, specifically 28 U.S.C. ยง 294. In essence, under normal conditions, the chief judge or judicial council of a circuit may assign a senior judge belonging to that circuit to perform any duty within the circuit that the judge is willing and able to perform. A senior district judge can be assigned to an appellate case, and a circuit judge can be assigned to preside over a trial. For courts that do not fall within a circuit, such as the United States Court of International Trade, the chief judge of that court can assign a senior judge of that court to perform any duty within the circuit that the judge is willing and able to perform.
In special cases, the Chief Justice can assign a senior judge to any court. This is referred to as an assignment by designation, and requires that a certification of necessity be issued by the appropriate supervisor of the court. For a circuit or district court, this supervisor is either the chief judge or the circuit justice of the circuit. For any other court, this supervisor is the chief judge of the court.
Retired justices can be assigned to any court (except the Supreme Court) the justice is willing to accept. Theoretically, a retired justice could also be assigned to act as Circuit Justice for a circuit, but this has never occurred.
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