A federal prisoner who seeks to challenge the legality of his conviction or sentence usually must do so in a motion under 28 U.S.C. §2255. Under the saving clause in §2255(e), however, a prisoner may file a petition for a writ of habeas corpus under 28 U.S.C. §2241 when it "appears" that a §2255 motion is "inadequate or ineffective to test the legality of his detention."

The question presented is whether a federal prisoner's challenge to his conviction or sentence under 28 U.S.C. §2255 is "inadequate or ineffective" – and thus the prisoner may raise that challenge in a habeas petition under 28 U.S.C. §2241 – because the challenge relies on a new decision of this Court that interprets and narrows the reach of a federal statute, and §2255(h) bars the prisoner from raising that challenge in a second or successive §2255 motion?

Whether a federal prisoner's challenge to his conviction or sentence under 28 U.S.C. §2255 is 'inadequate or ineffective' - and thus the prisoner may raise that challenge in a habeas petition under 28 U.S.C. §2241 - because the challenge relies on a new decision of this Court that interprets and narrows the reach of a federal statute, and §2255(h) bars the prisoner from raising that challenge in a second or successive §2255 motion