This paper presents a new category of criminal norms that are referred to as “instrumental crimes”. It is a from of anticipation through which the Spanish legislator punishes the preparation of crime incriminating evidence or processes to commit a crime in order to prevent new forms of crime. However, this decision is illegitimate because it is incompatible with constitutional principles. In that sense, maintaining those criminal norms in the code will require interpretation that conforms to the basic principles of criminal law.