Article 20
a. There shall be no crime and no punishment except under a law, and punishment only for acts committed subsequent to the effective date of the law providing for the same.
Article 31
The public rights and freedoms stated in this Constitution may only be regulated or limited by or in accordance with the law, and such regulation or limitation may not prejudice the essence of the right or freedom.
1. A person shall not be criminally responsible under this Statute unless the conduct in question constitutes, at the time it takes place, a crime within the jurisdiction of the Court.
2. The definition of a crime shall be strictly construed and shall not be extended by analogy. In case of ambiguity, the definition shall be interpreted in favour of the person being investigated, prosecuted or convicted.
3. This article shall not affect the characterization of any conduct as criminal under international law independently of this Statute.