"Prolonged detention" for Americans who may break a law?

Maddow: "How can a president speak the kind of poetry that president Obama does about The Rule of Law AND call for the power to indefinitely, preventively imprison people because they might commit crimes in the future? How can these things co-exist in the same man, even in the same speech? Well this brings us to the self-conscious awkwardly embarrassing part of this speech today. After condemning the Bush administration for what he called their 'ad-hoc legal strategy'; for trying to make things seem legal that patently weren't -- this is what Obama proposed."