Are democratic states permitted to denationalize citizens, in particular those whom they believe pose dangers to the physical safety of others? In this article, I argue that they are not. The power to denationalize citizens—that is, to revoke citizenship—is one that many states have historically claimed for themselves, but which has largely been in disuse in the last several decades. Recent terrorist events have, however, prompted scholars and political actors to reconsider the role that denationalization can and perhaps should play in democratic states, in particular with respect to its role in protecting national security and in supporting the global fight against terror more generally. In this article, my objective is to show that denationalization laws have no place in democratic states. To understand why, I propose examining the foundations of the right of citizenship, which lie, I shall argue, in the very strong interests that individuals have in security of residence. I use this formulation of the right to respond to two broad clusters of arguments: (1) those that claim that it is justifiable to denationalize citizens who threaten to undermine the safety of citizens in a democratic state or the ability of a democratic state to function as a democratic state, and (2) those that claim that it is justifiable to denationalize dual citizens because they possess citizenship status in a second country that is also able to protect their rights