It has been widely assumed that deterrence has little or no role to play in counterterrorism on the grounds that the threat of punishment is powerless to dissuade ideologically inspired terrorists. But an emerging literature in strategic studies argues, and aspects of contemporary American national security practice confirm, that this account misunderstands the capacity of deterrence to address current threats. In fact, a great deal of American counterterrorisma cluster of refinements to traditional deterrence theory that speaks to a world of asymmetric threats. Yet the emergence of new deterrence has been largely lost on lawyers, judges, and legal academics, resulting in significant gaps between the practice of national security in this area and the legal architecture ostensibly designed to undergird and oversee it. In particular, the legal framework of counterterrorismprecisely the two fields thought to converge in counterterrorism. In this Article, I debut in legal scholarship a sustained analysis of new deterrence and highlight its consequences for national security law, thus ushering in a serious reckoning for jurists with counterterrorism deterrence.