Cuius regio, eius religio

Cuius regio, eius religio (Ecclesiastical Latin: [ˈku.jus ˈre.d͡ʒi.o ˈe.jus reˈli.d͡ʒi.o]) is a Latin phrase which literally means "whose realm, his 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.