Introduction: beyond inter-state migration

How, if at all, do two increasingly topical debates – one concerned with the ‘migration’ of constitutional ideas and the other with the constitutionalization of supranational entities such as the European Union (EU) – connect? This is no simple question. Even if restricted to the traditional domain of inter-state movement, the debate on the migration of constitutional ideas is complex and contentious both empirically and normatively. It is empirically complex because the sources of the migrating constitutional ideas tend to be diffuse, hidden, or rhetorically overstated, and their reception mediated by and their meaning more or less subtly adjusted within the recipient legal system, both at the initial point of political and judicial interpellation and in their subsequent legal-cultural re-embedding. It is normatively contentious because there are such strong and well-rehearsed prima facie arguments both for and against migration – most of which, moreover, seem resistant to conclusive empirical proof or refutation – and, therefore, much disagreement about the circumstances and conditions, if at all, under which migration is acceptable or desirable.

The migration of constitutional ideas may be a ‘good thing’ where it counters parochial tendencies within national constitutional law, providing alternative models of constitutional virtue against which the domestic model can be evaluated, or, even if the most basic norms and ends of the recipient order are not challenged, supplying a broader range of constitutional techniques in the search for the optimal means towards the realizations of these norms or ends.