According to the Court’s case-law, a prohibition of discrimination can flow not only from enacted (written) Union law but also from (unwritten) general principles. Faced with the lack, or limited reach, of written non-discrimination law, the Court recognised the existence of two layers of general principles of equality, namely a general principle of equality tout court (i.e. a principle that is not linked to any discrimination ground) and a number of general principles of equality linked to particular discrimination grounds. In the resulting multi-level system, the Mangold line of case-law in particular raises questions not only about the relevance and function of the general principles of equality in the larger system of Union law, but als...