Hizb ut-Tahrir is an international Islamic organization that openly calls for restoration of the caliphate -- that is, the political union of Muslims worldwide in a single Sharia state ruled by the caliph. This means that the group is dedicated to subverting and destroying all governments not ruled by Islamic law, and as such it is banned in many countries. But not in the U.S., which has never shown any awareness on an official level of non-violent efforts to impose Sharia. They're once again coming to the Chicago area to hold their Caliphate Conference: it will be held on June...