A separate, older statute that empowers federal courts to issue mandamus and other extraordinary writs in aid of their jurisdiction.

The All Writs Act, codified at 28 U.S.C. § 1651, authorizes federal courts to "issue all writs necessary or appropriate in aid of their respective jurisdictions." Unlike Section 1361, which specifically targets actions against federal officers, the All Writs Act is a general grant of authority that courts of appeals frequently rely on when reviewing lower court conduct.

Mandamus to control lower courts

The most common modern use of the All Writs Act in the mandamus context is a petition asking a court of appeals to direct a district judge to act — for example, to rule on a long-pending motion, to correct a clear legal error before final judgment, or to address a discovery dispute that cannot wait for an ordinary appeal.

"Necessary or appropriate in aid of jurisdiction"

Courts read this phrase to mean the writ must be tied to protecting the court's own eventual ability to exercise its jurisdiction effectively — not simply a tool for correcting any error a party finds objectionable. This framing reinforces why appellate mandamus against a district judge remains rare.

Interaction with Federal Rule of Appellate Procedure 21

While the All Writs Act supplies the underlying authority, Federal Rule of Appellate Procedure 21 supplies the actual procedure for filing a mandamus petition in a court of appeals. The two work together: the statute grants the power, and the rule tells a petitioner how to invoke it.

A tool of last resort, even among mandamus remedies

Appellate courts frequently describe All Writs Act mandamus as reserved for "exceptional circumstances amounting to a judicial usurpation of power" — language that signals just how far removed this remedy is from an ordinary appeal.