Federal law allows a district court to order the civil commitment of a mentally ill, sexually dangerous federal prisoner beyond the date he would otherwise be released. 18 U. S. C. §4248. The Government instituted civil-commitment proceedings under §4248 against respondents, each of whom moved to dismiss on the ground, inter alia, that, in enacting the statute, Congress exceeded its powers under the Necessary and Proper Clause, U. S. Const., Art. I, §8, cl. 18. Agreeing, the District Court granted dismissal, and the Fourth Circuit affirmed on the legislative-power ground.
Held: The Necessary and Proper Clause grants Congress authority sufficient to enact §4248. Taken together, five considerations compel this conclusion. Pp. 5–22.
