Part IV Fundamental Liberties
Article 11
Protection Against Retrospective Criminal Laws and Repeated Trials
(1) No person shall be punished for an act or omission which was not punishable by law when it was done or made, and no person shall suffer greater punishment for an offence than was prescribed by law at the time it was committed.
Nullum crimen sine lege
Nulla poena sine lege
EDIT.