Cuius regio, eius religio

Cuius regio, eius religio (ˈkujus ˈregi.o ˈejus reˈligi.o) is a Latin phrase which literally means "whose realm, their religion" – meaning that the religion of the ruler was to dictate the religion of those ruled. This legal principle marked a major development in the collective (if not individual) freedom of religion within Western civilization. Before tolerance of individual religious divergences became accepted, most statesmen and political theorists took it for granted that religious diversity weakened a state – and particularly weakened ecclesiastically-transmitted control and monitoring in a state. The principle of "cuius regio" was a compromise in the conflict between this paradigm of statecraft and the emerging trend toward religious pluralism (coexistence within a single territory) developing throughout the German-speaking lands of the Holy Roman Empire. It permitted assortative migration of adherents to just two theocracies, Roman Catholic and Lutheran, eliding other confessions. At the Peace of Augsburg of 1555, which ended a period of armed conflict between Roman Catholic and Protestant forces within the Holy Roman Empire, the rulers of the German-speaking states and the Holy Roman Emperor, Charles V, agreed to accept this principle. In practice the principle had already been implemented between the time of the Nuremberg Religious Peace of 1532 and the 1546–1547 Schmalkaldic War. Now legal in the de jure sense, it was to apply to all the territories of the Empire except for the Ecclesiastical principalities and some of the cities in those ecclesiastical states, where the question of religion was addressed under the separate principles of the reservatum ecclesiasticum and the Declaratio Ferdinandei, which also formed part of the Peace of Augsburg. This agreement marked the end of the first wave of organized military action between Protestants and Catholics; however, these principles were factors during the wars of the 1545–1648 Counter-Reformation.