President Barack Obama has convened a multiagency taskforce whose remit includes considering whether the U.S. should develop a new system of ‘preventive detention’ to hold terrorist suspects. American scholars and advocates who favor the establishment of a 'preventive detention' regime in the United States frequently point to comparative examples in support of their argument. At the same time, advocates and scholars opposed to the introduction of such a system often turn to comparative law to bolster their arguments against ‘preventive detention.’ Thus far, however, the scholarship produced by both sides of the debate has been limited in two key respects. Firstly, there have been definitional inconsistencies in the literature - the term 'preventive detention' has been used over-broadly, to describe a number of different kinds of detention, with very little acknowledgment of the fundamental differences between these alternative regimes. Secondly, the debate has been narrow in scope - focusing almost exclusively on 'preventive detention' in three or four other (overwhelmingly Anglophone) countries. This Article seeks to advance the debate about ‘preventive detention’ by moving beyond each of these limitations. First, the Article defines, analyzes, and differentiates between the different kinds of ‘preventive detention.’ Second, the Article broadens the scope of the debate by comparing the systems of terrorism-related 'preventive detention' in use in thirty-two different countries. The Article constructs a taxonomy of 'preventive detention,' based on core principles of international law, to distill the key attributes of the preventive detention regimes in each of the countries surveyed. Using the taxonomy, the Article proposes that there are three different overarching frameworks used to detain terrorist suspect detainees: (1) the pre-trial detention framework; (2) the immigration detention framework; and (3) the national security detention framework. This Article proposes that U.S. policymakers contemplating possible future approaches to the detention of suspected terrorists should move beyond the inapposite and misleading question of whether to introduce 'preventive detention,' and should instead determine which of these three frameworks offers the most appropriate approach to the detention of terrorist suspects. The Article concludes with the argument that, once this determination is made, U.S. policymakers should conclude that a version of the pre-trial detention framework approach would be most suited for use in the United States.