This book investigates nullum crimen sine lege as European principle in its interpretation by the European Court of Human Rights. The research focuses on the role of foreseeability as a solution to the legality issues raising from judge-made law in criminal law. The rationale and application of foreseeability in ECt HR case-law are scrutinised, trying to extract its main development paths. Current solutions adopted by civil law States (Italy and Germany) are analysed also considering the theoretical foundations of ncsl. Moreover, the role of foreseeability in EU law is considered, as an example of an effectiveness-oriented legal order. In the end, future perspectives for the implementation of the principle of foreseeability are analysed.