4.2.2 The significance of these cases for Union law

147. Probably one of the most earth-shattering novelties from Mangold was that the Court of Justice launched the principle of non-discrimination on the basis of age as a general principle of Union law.1 Another considerably epoch-making novelty is that national courts are obliged to, in certain cases, review the compatibility of provisions of national law against this particular general principle of Union law. And, as confirmed in Kücükdeveci and emphasised in Dansk Industri, the consequence of a provision of national law being incompatible with the general principle of the prohibition of age discrimination is that the provision of national law has to be disapplied in the case at hand.

The judgments in Mangold, Kücükdeveci and Dansk Industri have been subject to an avalanche of – various degrees of – criticism2, particularly concerning the nagging question which rules of Union law can be invoked by a private party in order to disapply a provision of national law in horizontal proceedings.