Scholars generally write about popular sovereignty in terms of the expression of the people’s will alone. They do not treat territory as part of the definition of popular sovereignty. My work on Secession and the Prevalence of Both Militant Democracy and Eternity Clauses Worldwide published in the Cardozo Law Review reveals that popular sovereignty is a territorial concept. In this paper, I argue that the overwhelming majority of world constitutions are not terribly concerned with immigration or emigration of people. They are also not concerned with the redrawing of borders alone. Rather, constitutions treat the combined challenge of withdrawal of citizens with territory as a revolutionary act in the Kelsenian sense. Such an act requires a new constitutional beginning by both the seceding and the remaining populations. The article thus explores the meaning of popular sovereignty as a territorial concept protected from constitutional change from within the system.