Whether a district court has jurisdiction under section 2241 to review a claim that a federal prisoner's sentence is invalid in light of an intervening and retroactively applicable decision of this Court, where circuit precedent foreclosed the claim at the time of the prisoner's prior section 2255 motion

QUESTION PRESENTED A person in federal custody ordinarily may collaterally challenge the legality of his detention only once, by filing a motion to vacate or set aside his conviction or sentence under 28 U.S.C. § 2255. Under section 2255(e)’s saving clause, however, such a person may file an application for habeas corpus under 28 U.S.C. § 2241 when it “appears” that a section 2255 motion is “inadequate or ineffective to test the legality of his detention.” The question presented is: Whether a district court has jurisdiction under section 2241 to review a claim that a federal prisoner’s sentence is invalid in light of an intervening and retroactively applicable decision of this Court, where circuit precedent foreclosed the claim at the time of the prisoner’s prior section 2255 motion. @)