The Supreme Court has announced that it will hear arguments over a federal law that allows the government to confine "sexually dangerous" prisoners in mental hospitals after they've served out their sentences. According to the Department of Justice, 95 federal prisoners have been "identified as possible candidates for post-sentence detention." Back in January, the 4th Circuit Court of Appeals struck down the law as unconstitutional. The 4th Circuit's justification:
The Constitution does not empower the federal government to confine a person solely because of asserted "sexual dangerousness" when the Government need not allege (let alone prove) that this "dangerousness" violates any federal law.
A commenter at Sentencing Law and Policy (linked above) points out probably the strangest element of the law in question (18 USC 4248): It allows the government to detain "sexually dangerous" persons regardless of their crime:
Section 4248 does not require that the potential committee has ever been convicted of a federal sex offense, or indeed ANY sex offense. All it requires (on this issue) is that the govt prove, by clear and convincing evidence, that the person has at some time in his or her life engaged in child molestation or sexually violent conduct (both as defined by BOP regs).