Between the 12th and 13th centuries, the “Regnum Siciliae” emerged in Europe as an institution that gave strong political cohesion, under the idea of a unitary public power, to a vast territorial area with a multi-ethnic and multi-religious population. In textual and iconographic representations, the sovereignty of the kings of Sicily is placed at the crossroads of the biblical conception of kingship and the idea of “maiestas” inherited from the Romano-Byzantine tradition. From Roger II to Frederick II, royal legislation represented a primary instrument of government of the Kingdom. Above the recurring conflicts be- tween the Kingdom and the Papacy, religion and the idea of the alliance between throne and altar were conceived as fundamental instruments of government.