Constitutional pluralism or constitutional unity? An empirical study of international commitment (1945-2007)

This article asks whether international law is moving towards a more unified constitutional order or whether differentiated types of constitutional processes are emerging. We study the sequencing and ratification pace of 32 'quasi-constitutional' international agreements containing procedural guidelines for inter-state relations and fundamental human rights provisions for individuals drawn up between 1945 and 2007. We do so in a comparative and quantitative fashion applying sophisticated statistical tools, namely event history techniques combined with counting processes. On the basis of our multi-treaty framework, the findings do not lend support to a unified and quick process of global constitutionalisation. Rather, they provide evidence for the idea of a 'multi-speed globe' of differentiated constitutionalisation. We also make a first attempt to study antecedents to global constitutionalisation. Our findings show that processes of global constitutionalisation vary across regime types and world regions (while there is no effect for new and old states).