 Administrative Procedure Act.The authority of the United States district courts (trial courts) to issue mandamus has been expressly abrogated by Rule 81(b) of the Federal Rules of Civil Procedure, but relief in the nature of mandamus can be had by other remedies provided for in the Rules, where provided by statute, or by use of the District Court's equitable powers.In the context of "mandamus" from a United States Court of Appeals to a United States District Court, the Supreme Court has ruled that the appellate courts have discretion to issue "mandamus" to control an abuse of discretion by the lower court in unusual circumstances, where there is a compelling reason not to wait for an appeal from a final judgment.