PART TWO - FUNDAMENTAL RIGHTS AND DUTIES
CHAPTER TWO- RIGHTS AND DUTIES OF THE INDIVIDUAL
XIII. Provisions Relating to the Protection of Rights
C. Principles Relating to Offences and Penalties
No one shall be punished for any act which does not constitute a criminal offence under the law in force at the time committed; no one shall be given a heavier penalty for an offence other than the penalty applicable at the time when the offence was committed.
Non-retroactivity
Nullum crimen sine lege
Nulla poena sine lege
EDIT.