The relations between the Catholic Church and the state have been constantly evolving with various forms of government, some of them controversial in retrospect. In its history, the Church has had to deal with various concepts and systems of governance, from the Roman Empire to the medieval divine right of kings, from nineteenth- and twentieth-century concepts of democracy and pluralism to the appearance of left- and right-wing dictatorial regimes. The Second Vatican Council's decree Dignitatis humanae stated that religious freedom is a civil right that should be recognized in constitutional law.