EU being a new creature of international law, certain amendments of the adherence rules had to be made to allow the EU’s accession to the ECHR. The treaties of the Union have been modified as well in order to include a provision that obliges the EU to accede to the ECHR as a legal basis for the act of accession. This article of the Treaty on the European Union contains also a limitation:
“Such accession shall not affect the Union’s competences as defined in the Treaties”. In the Opinion 2/13 from 18 December 2014, the CJEU interprets the art 6(2) as expressing a guarantee that the accession shall not restrict tasks and powers assigned to the CJEU by the Treaties. The neuralgic point of concern appears to be the art. 344 TFEU that obliges the Member States to submit disputes on the interpretation and application of the Treaties exclusively to the CJEU.
Member States and their courts, including the constitutional courts deal constantly with the issue of accurate interpretation and correct application of EU law and the solution to the problem of coherent and effective application relies on the preliminary ruling mechanism supported by art. 267 TFEU.