28 U.S.C. §2241
Section 2241 is a post-conviction remedy that extends to convicted persons in custody pursuant to the judgment of any federal court. This remedy is a civil action, separate from the criminal proceedings that resulted in the conviction. In general, a conviction or sentence may be challenged under §2241 to the same extent that it may be challenged in a proceeding under §2254. As a practical matter, then, a person convicted in federal court rarely will be able to invoke §2241 to fight for justice.