Chapter 2 - Basic rights and liberties
Section 8 - The principle of legality in criminal cases
No one shall be found guilty of a criminal offence or be sentenced to a punishment on the basis of a deed, which has not been determined punishable by an Act at the time of its commission. The penalty imposed for an offence shall not be more severe than that provided by an Act at the time of commission of the offence.
Non-retroactivity
Nullum crimen sine lege
Nulla poena sine lege
EDIT.