CONSTITUTION OF CYPRUS
ARTICLE 12
1. No person shall be held guilty of any offence on account of any act or omission which did not constitute an offence under the law at the time when it was committed; and no person shall have a heavier punishment imposed on him for an offence other than that expressly provided for it by law at the time when it was committed.
Non-retroactivity
Nullum crimen sine lege
EDIT.