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
3. No sentence or security measure shall be applied unless it is expressly sanctioned in a pre-existing law.
4. No one shall be the object of a sentence or security measure that is more severe than those provided for at the moment of the conduct in question, or at that at which the prerequisites for the application of such a measure were fulfilled. However, criminal laws the content of which is more favourable to the defendant shall be applied retroactively.
EDIT.