Schedule B - Constitution Act, 1982 (79)

PART I - Canadian charter of rights and freedoms

Legal Rights

11. Any person charged with an offence has the right

...
g) not to be found guilty on account of any act or omission unless, at the time of the act or omission, it constituted an offence under Canadian or international law or was criminal according to the general principles of law recognized by the community of nations;

Article 11
Jurisdiction ratione temporis
2. If a State becomes a Party to this Statute after its entry into force, the Court may exercise its jurisdiction only with respect to crimes committed after the entry into force of this Statute for that State, unless that State has made a declaration under article 12, paragraph 3.

Article 24
Non-retroactivity ratione personae
1. No person shall be criminally responsible under this Statute for conduct prior to the entry into force of the Statute.
2. In the event of a change in the law applicable to a given case prior to a final judgement, the law more favourable to the person being investigated, prosecuted or convicted shall apply.