Is the horizontal application of general principles ultra vires? Dialogue and conflict between supreme European courts in Dansk Industri

The evolution of the case law on the principle of non-discrimination (Mangoldand Kücükdeveci) has shown a clear trend towards its application to litigation between private parties. This contribution aims to discuss one of the latest developments in the case law of the Court of Justice, Dansk Industri, and its subsequent application by the Danish Supreme Court, the national Court which requested the preliminary ruling. The joint analysis of the decisions of the Court of Justice and of the Danish Court reveals that this trend towards the horizontal application of the principle of non-discrimination has been rejected, and that even fundamental elements of the EU constitutional legal order cannot escape the ultra viresreview of national Supreme Courts. Will the Court of Justice follow –for the future -the line of the defence of horizontal direct effect of the principle, or will it choose a more inclusive solution akin to the Taricco IIjudgement?