The great era of constitutionalism spans from the American revolution of 1776 to the octroyed French constitution of 1814. Yet, the European constitutional mechanisms and way of reasoning can be traced much further back. This volume displays the need to expand, restrain and at the same time legitimise state power from the 12th century and beyond the great era of constitutionalism in order to demonstrate its historical reach. The Church was an early example of a state-like and centralised power, and thus contributed greatly to the development of a state organised Europe. This volume examines the Church as a driving force behind constitutional reasoning and as a developer of constitutional practice throughout the Middle Ages. Feudal law, with its contractual based system of rights and duties, could regulate society on several levels and thus was another source for constitutional reasoning and practices.