General provision
Section I
Criminal Legislation
CHAPTER 2
ACTION OF THE CRIMINAL LAW
Article 10. Action of the criminal law in time
10.1. The criminality and punish of action (action or inaction) shall be determined by the criminal law, exercised during commitment of this action (action or inaction). No one shall be applied to criminal liability for action, which was not admitted as a crime at the time of committing it.
Non-retroactivity
Nullum crimen sine lege
EDIT.