Man fails to update his sex offender registration when he moves abroad, so he is sentenced to 673 days. While serving his sentence, gov’t deems him sexually dangerous person, subjects him to civil commitment. But wait! The Supreme Court later holds failing to update one’s registration if they move abroad is not a crime; man’s conviction is vacated. Free him? Fourth Circuit: No. Dissent: There’s a constitutional problem with keeping a man in custody for seven years without a valid conviction.