This is a commentary on the latest contribution of the Court of Justice of the EU to the development of EU citizenship, the Lounes case. A preliminary request brought by the UK High Court concerning an amendment made to the national regulation implementing Directive 2004/38, this dual nationality case highlights the differences between EU migration law and that of the UK. In this sense, it is also indicative of what is to be expected once EU citizens’ rights are no longer protected by EU law and the Court of Justice but by the EU-UK Withdrawal Agreement after Brexit