This collection brings together some of the most influential sociologists of law to confront the challenges of current transnational constitutionalism. It shows the constitution appearing in a new light: no longer as an essential factor of unity and stabilisation but as a potential defence of pluralism and innovation. The first part of the book is devoted to the analysis of the concept of constitution, highlighting the elements that can contribute from a socio-legal perspective, to clarifying the principle meanings attributed to the constitution. The study goes on to analyse some concrete aspects of the functioning of constitutions in contemporary society. In applying Luhmann’s General Systems Theory to a comparative analysis of the concept of constitution, the work contributes to a better understanding of this traditional concept in both its institutionalised and functional aspects. Defining the constitution’s contents and functions both at the conceptual level and by taking empirical issues of particular comparative interest into account, this study will be of importance to scholars and students of sociology of law, sociology of politics and comparative public law.