Nulla poena sine lege

Nulla poena sine lege means that no penalty may be imposed without a legal basis. In Swiss criminal law it expresses the legality principle: offences and sanctions must be defined by law with sufficient clarity, and criminal liability may not be created retroactively to the detriment of the accused. The maxim also supports restraint in analogy and interpretation where they would expand punishment. It safeguards democratic lawmaking, foreseeability, and protection against arbitrary penal power.