Nullum Crimen Sine Lege
Definition - What does Nullum Crimen Sine Lege mean?
Nullum crimen sine lege is a Latin term that literally translates as "no crime without law." As a legal principle, nullum crimen sine lege establishes that a person cannot be punished criminally for an act that was not considered a crime at the time of its commission. Even if a law is eventually passed that makes an act criminal, it is not punishable if the the act was committed before the inception of the law. If the act occurs after the law's inception, then it can already be considered a criminal act.
Justipedia explains Nullum Crimen Sine Lege
Nullum crimen sine lege is a legal standard that must be observed when dealing with criminal acts that were committed before the inception of the laws that criminalized them. In these instances, the person committing the act cannot be punished criminally because there is no crime. A popular example involved the imposition of the alcohol prohibition. By the principle of nullum crimen sine lege, persons who drank alcohol before the inception of the law did not commit a crime even though it was eventually criminalized by said law.