EU law is always supreme. If a law in France violates EU law, then any foreign EU national in France with standing can use French courts to have the law annulled.
> The revolutionary case of NV Algemene Transport-Expedite Onderneming Van Gend en Loos v Nederlandse Administratie der Belastingen (9), addressed this matter, but also the issue of supremacy. In regard to Article 12 EEC (now Article 30 TFEU), The ECJ held ‘the objective of the EEC treaty… implies that this treaty is more than an agreement which merely creates obligations on individuals but is also intended to confer upon them rights’ (10), giving the article direct effect. This permits the rights of individuals and organisations to be enforceable in national courts, as a way of creating uniformity amongst member states to maximise the efficiency and application of EU law, despite the fact that the treaty articles generally regulated trade between member states [0].
This is known as the Doctrine of Direct Effect. The ECJ is effectively a 'supreme court' for the EU.
> The revolutionary case of NV Algemene Transport-Expedite Onderneming Van Gend en Loos v Nederlandse Administratie der Belastingen (9), addressed this matter, but also the issue of supremacy. In regard to Article 12 EEC (now Article 30 TFEU), The ECJ held ‘the objective of the EEC treaty… implies that this treaty is more than an agreement which merely creates obligations on individuals but is also intended to confer upon them rights’ (10), giving the article direct effect. This permits the rights of individuals and organisations to be enforceable in national courts, as a way of creating uniformity amongst member states to maximise the efficiency and application of EU law, despite the fact that the treaty articles generally regulated trade between member states [0].
This is known as the Doctrine of Direct Effect. The ECJ is effectively a 'supreme court' for the EU.
[0]: https://www.lawteacher.net/free-law-essays/european-law/eu-l...