This book examines the conditions under which a constitutional regime can be considered legitimate from a democratic perspective. The book argues that only a regime that provides an outlet for constituent power to manifest from time to time can ever come to enjoy democratic legitimacy. In so doing, it advances a democratic constitutional theory, one that combines a strong or participatory conception of democracy with a weak form of constitutionalism. Under this view, a democratically legitimate constitutional regime must remain permanently open to re-constitution through highly participatory procedures.