When are religious employers exempt from the prohibition of discrimination (i.e., when can they discriminate against non-adherents)? The European Union (EU) Equality Framework Directive exempts religious employers from the prohibition of religious discrimination, but the scope of the religious ethos exemption is disputed and its interpretation by the Court of Justice of the European Union (CJEU) in Egenberger and IR v JQ has been criticised for being ultra vires and for disrespecting the constitutional identities of the EU Member States. This article clarifies the religious ethos exemption, by examining the underlying legal and normative issues that determine its scope. It shows that the scope of the exemption depends not just on the Framework Directive but also on the relationship between EU law and national constitutional law and that between EU law and international law. Thus, this article not only provides clarity regarding the religious ethos exemption, but also uses these judgements as an opportunity to revisit these related constitutional issues, and in particular the role of the CJEU and EU legislature in defining the place of national constitutional identity in EU law.