Abstract
The contribution reflects on the principle of legality in substantive and formal criminal law. Firstly, the principle of legality (nullum crimen sine lege) and its manifestations (certa, stricta, scripta, praevia) are discussed.
Furthermore, the contribution reflects on the principle of due and lawful process (nullus processus criminalis sine lege), which can be understood as the most important principle of criminal proceedings. Both discussed principles are the backbone of criminal law.
They have many theoretical connections and practical implications.