Understanding Legal Evolution Through Constitutional Theory: The Concept of Constitutional (In-)Flexibility

__Abstract__ Why do legal arrangements for the institutions of government (legislative, executive, judicial branches) in Western liberal democracies develop faster, or in a different way, in one jurisdiction in comparison to another? In this article, it is argued that constitutional theory can help us understand the development of these legal institutional arrangements, for example in light of of the changing role of national highest courts in the the globalised legal context. For this purpose, the concept of constitutional (in-)flexibility is introduced, which can explain how national constitutional frameworks enable or constrain the integration of normative changes in national legal systems. Four elements encompassed by this concept are identified: the detail of constitutional norms, the modalities for revising the national Constitution, the approach to legal argumentation taken by interpreters of the Constitution, and the influence attributed to international law within the national legal system. This analytical framework is applied to the illustrative case of judicial globalisation - concerning, inter alia, the judicial use of non-binding foreign law - to explain similarities and differences concerning the way in which changes affecting the functioning of national highest courts are integrated within different legal systems. This analysis, in turn, yields some insight into the further development of constitutional theory in the era of globalisation