The purpose of the preliminary reference procedure is to ensure a uniform application and interpretation of Community law across all the Member States, including European fundamental rights as enshrined in the Charter of Fundamental Rights of the European Union. The entry into force of the Charter has reinforced the authority of the Court of Justice of the European Union (CJEU) in the field of fundamental rights adjudication. But the Charter may also be a new source of conflicts between the jurisdiction of the CJEU and the jurisdiction of national constitutional courts. Indeed, compliance with the indirect rulings over national law contained in the CJEU decisions became something logical for the national ordinary courts from the beginning of the integration process, but it was not the same for national constitutional courts. Most of them have always disliked the idea of asking for the CJEU's opinion on a conflict of law involving national constitutional provisions. The CJEU succeeded in establishing a legal doctrine through principles of Community law—supremacy and direct effect being the pioneers—that meant a material constitutionalization of the European Union (EU) law system. And for the national constitutional courts, such an understanding of EU law made a rival of the CJEU.
Supremacía de la constitución versus primacía del derecho de la UE en materia derechos fundamentales: concordancias y discordancias entre el tribunal constitucional y el tribunal de justicia de la UE en el asunto Melloni
