The principle of the rule of law is a well-established notion at the core of modern constitutionalism and the undisputed building block of democratic governments. This principle is characterized by the breadth of its scope, the difficulty to strictly define its content, and the increasing possibility of a more or less broad interpretation. This explains the wide-ranging debate on the rule of law which has been developed over time with significant contributions from several disciplines, including philosophy, constitutional law, and international law.