The indefinite detention of prisoners at Guanta ́namo Bay Naval Base raises serious concerns about what rights those detainees are entitled to and whether detainees will have the power to exercise them. How, for instance, could a detainee pursue a meaningful appeal of a decision of the Combatant Status Review Tribunal without effective assistance of counsel? How could a detainee challenge his detention when the U.S. government renders that detainee to foreign custody? The All Writs Act, a broad and historic statute originally codified in the Judiciary Act of 1789, provides that “courts may issue all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law.” The Act grants the courts equitable power to issue injunctions that ensure that litigants’ substantive rights are not frustrated by interstices in the applicable law. It is in this Act that district courts exercising habeas corpus jurisdiction found detainees’ rights to effective assistance of counsel and thirty days’ notice prior to transfer to foreign custody. While the Military Commissions Act stripped the courts of habeas jurisdiction with respect to alien enemy combatants, the equitable power granted by the All Writs Act can attach to any jurisdiction, including the appellate power given to the D.C. Circuit Court of Appeals to review determinations made at Guanta ́namo Bay. This Note provides a roadmap that courts should apply when considering whether to issue an All Writs Act injunction, and concludes that such injunctions are not only permissible but also an appropriate and important exercise of the courts’ power.