Two weeks ago, the New York state legislature passed a bill providing for the continued incarceration of certain sex offenders after they have completed their prison sentences, if these individuals are thought to present a risk of re-offending. On the 14th, governor Eliot Spitzer signed it into law. Thus, New York is the twentieth state to adopt some form of "civil confinement" (which, to my shame, includes my chosen state of residence, Washington). This kind of practice, of locking people up on the basis of crimes they might commit, but have not actually committed, was ruled constitutional by the Supreme Court in 1997, in Kansas v Hendricks, in which then-Chief Justice William Rehnquist (in)famously asked "So what's the State supposed to do, just wait till he goes out and does it again?"
Well, frankly, yes. At least, given the current state of the American criminal justice system, which is founded upon the notion that the state can punish a criminal only for offenses he has actually committed, and that once said convict has served his sentence, he has "paid his debt to society" and starts out anew with a clean slate. You can argue that that is a fiction, but in doing so, you are admitting that imprisonment does not work as a means of "correcting" offenders. And if that is the case, we need put some effort into coming up with something that does work, instead of coming with stuff like sex offender registries, exclusion zones and civil confinement; measures designed to, in effect, impose on offenders who have already completed their sentences additional punishment for crimes they might commit.