Part I Fundamental rights and duties
Section II Rights, Freedoms, and Safeguards
Chapter I Personal Rights, Freedoms, and Safeguards
Article 29 Application of Criminal Law
1. No one shall be sentenced under the criminal law unless the action or omission in question is punishable under the terms of a pre-existing law, nor shall any person be the object of a security measure unless the prerequisites therefore are laid down by a pre-existing law.
2. The provisions of the previous paragraph shall not preclude the punishment up to the limits laid down by internal Portuguese law of an action or omission which was deemed criminal under the general principles of commonly recognised international law at the moment of its commission .
Non-retroactivity
Nullum crimen sine lege
EDIT.