Nullum Crimen Sine Lege

Nullum Crimen Sine Lege is a legal principle that states an individual cannot be prosecuted for a crime unless it has been defined as such by law. This principle underscores the importance of clarity and certainty in the law, ensuring that individuals are aware of what constitutes a criminal act.

The maxim has roots in Roman law, where it served to protect citizens from arbitrary prosecution and punishment. It has since been enshrined in many legal systems around the world, including the modern penal codes of various jurisdictions.

In contemporary law, Nullum Crimen Sine Lege plays a crucial role in safeguarding individual liberty by ensuring that laws are not applied retroactively. It is foundational in criminal law, requiring statutes to be clear and publicized in order for individuals to understand the prohibited conduct.

• A person cannot be convicted of theft if the conduct they engaged in was not classified as theft at the time it occurred.
• If a law is enacted prohibiting a specific action after a person committed that act, they cannot be prosecuted under that new law.

• Kolender v. Lawson, 461 U.S. 352 (1983)