Résumé : This e-learning course answers 10 key questions on the general principles of EU law as applied by the CJEU to criminal justice and its interpretation of concepts of substantive and procedural criminal law.A growing body of case law has been developed by the European Court of Justice on the legal instruments dealing with judicial cooperation in criminal matters (most notably the European Arrest Warrant and the Convention implementing the Schengen Agreement). There is also a broader body of case law that could have an impact in national criminal proceedings in terms of how general principles of EU law (e.g. on free movement, asylum) are applied to criminal justice and how different fundamental principles of EU law are balanced (esp. mutual recognition and fundamental rights). This e-learning course analyses the interpretation of substantive and procedural criminal law concepts. It is a tool designed to facilitate the use by criminal justice practitioners of the broader CJEU case law in criminal cases in which EU law might come into play. The content is structured in 10 key questions, complemented by a brief reminder of the EU legislative competence and the role of the CJEU in criminal matters. It also features a video presentation by Judge Lars Bay Larsen of the CJEU.