Chapter Two – Fundamental Rights and Freedoms
Part Seven: The Right to Judicial and Other Legal Protection
Article 50
(6) The criminal liability of a deed is assessed, and punishment is meted out, according to the law valid at the time when the offense was committed. A more recent law will be applied if it is more favorable for the perpetrator.
Non-retroactivity
Nullum crimen sine lege
Nulla poena sine lege
EDIT.