Nulla poena sine lege

Nulla poena sine lege (Latin for "no penalty without law", Anglicized pronunciation: /ˈnʌlə ˈpnə ˈsn ˈl/ NULPEE-nə SY-nee LEE-jee) is a legal formula which, in its narrow interpretation, states that one can only be punished for doing something if a penalty for this behavior is fixed in criminal law. Variant nullum crimen sine lege ("no crime without law") establishes that conduct is not criminal if not found among the behavior/cirumstance combinations of a statute. The other interpretations of the formula include the rules prohibiting retroactive criminalization and prescribing laws to be strictly construed.[1]

Despite the use of Latin language and brocard-like[2] appearance, the formula was mostly born in 18th century liberalism (some elements of non-retroactivity of laws and limiting the punishment to the one prescribed in the statute date back to Roman times).[3] This principle is accepted and codified in modern democratic states as a basic requirement of the rule of law.[4] It has been described as "one of the most 'widely held value-judgement[s] in the entire history of human thought'".[5]