Judicial dialogue on data retention laws: A breakthrough for European constitutional courts?

In 2006 the European Union (EU) adopted a directive which imposed on telecommunication operators an obligation to store all the telecommunication data (data retention) and provide access to retained data to state authorities in order to combat serious crime. The new legislation had to been implemented by all EU Member States. Immediately after the directive was issued, it triggered controversy. Substantial reservations against this measure had been confirmed by five European constitutional courts already within the first eight years since its introduction. In 2014 the Court of Justice of the European Union (CJEU) also acknowledged those reservations. Since then, further European constitutional courts invalidated domestic legislation on data retention. This jurisprudence posed a unique research opportunity to verify whether a genuine judicial dialogue within the varied legal systems occurred in the EU. In this article we analyze jurisprudence of constitutional courts, CJEU, and the European Court of Human Rights (ECtHR) on data retention. We identify interactions between domestic and international standards of privacy protection. The main method employed is a comparative study of all the judgments (following their translation) along with a simultaneous analysis of the common EU regulatory framework that all of those judgments challenged. A pivotal finding was an identification of three basic models clearly describing approaches taken by the constitutional courts involved. As the basis for our models, we used the approach of constitutional courts to two pan-European courts: ECtHR and CJEU. We claim that the analyzed jurisprudence constituted an important building block in the construction of a constitutional tradition relating to the protection of privacy based on the European Convention of Human Rights. Existence of this tradition led to the 2014 CJEU judgment (and to subsequent judgments of national constitutional courts).