SECTION II
HUMAN RIGHTS AND FREEDOMS
Chapter II
Human rights and freedoms
Article 28
1. A law establishing or aggravating the liability of a person shall not have retroactive force. No one may be held guilty of any act which did not constitute a criminal offence at the time when it had been committed. In the event that after committing an offence, provision is made for the removal of the liability or imposing of a lighter penalty, then the new law shall be applied.
EDIT.