EU protection of the substantive criminal law principles of guilt and ne bis in idem under the Charter of Fundamental Rights: Underdevelopment and overdevelopment in an incomplete criminal justice framework

European Union (EU) law is increasingly influencing the substantive criminal law of the member states. In this area of law – in which criminal liability and subsequent punishment are at stake – protection of fundamental rights is indispensable, as a result of which means the Charter has great potential relevance. This article examines the protection of fundamental rights by Union law in the field of substantive criminal law since the Charter has become binding and compares it to the protection offered by the European Court of Human Rights (ECtHR). The article focuses on two fundamental rights that rule substantive criminal law: the principle of guilt and the ne bis in idem principle. It holds that EU law still does not provide a full foundation to both principles of criminal substantive law. Given the particular nature of EU law, the practice of the institutions in substantive criminal law, and the current case law of the European Court of Justice and the ECtHR, we argue that the current level of protection in these parts of the criminal law is insufficiently convincing. Progress needs to be made in the recognition and appreciation of the principle of guilt, while the ne bis in idem principle might be overextended