A huge scholarly output has problematized the topic of the post-­sovereignty condition in general and the emergence of the European Union as a ‘polycentric, pluri-systemic, multi-state legal order’ in particular. If sovereignty is the supreme legal authority of the nation to give and enforce the law within a certain territory without exterior interference, we are witnessing a transformative decline of this authority on a hitherto unprecedented scale with the bulk of member states' statutes now originating in European harmonization directives or framework decisions. This transformation has especially raised concern with respect to the democratic process and the self-determination of the member states.

However, this chapter does not concern itself with these aspects of the transformation(s) but focuses instead on the possible consequences for the Rechtsstaat, the continental conceptualization of the rule of law. The choice of subject matter follows from the Rechtsstaat's undeniable sociological importance and normative potential in various European legal traditions. On the one hand, there is the concept's centrality as the mutual articulation of two fundamental principles of political philosophy, the state and the law, whereby the law builds the very structure of the state instead of just being an external limitation to it. On the other hand, the Rechtsstaat is widely considered to be a safeguard against state enchroachment on the civil and political rights of the individual.