In the development of the enquiry and investigation of criminal proceedings under Law 906 of 2004, means of evidence were created that affect fundamental rights such as freedom, life, good name, entity, private property, and freedom of movement, among others. The application of such means can be ordered by the Attorney General’s Office without prior legal control by a supervisory judge. Thus, this research is based on the question: Should prior control by the judge of guarantees be necessary in the acts of enquiry and investigation provided for in Law 906 of 2004? This article will give a clear and convincing answer, using a legal-qualitative method of interpretation through which the need for prior control by the judge in acts such as those in Book II (investigation techniques and investigation of evidence and the evidential system), Title I (the investigation and the investigation) will be studied and recognised. In addition, the need for the judge’s intervention will be analysed and justified for means such as search and seizure, the retention of correspondence, the interception of communications, the recovery of information left behind when surfing the internet or other similar technological means, the surveillance and monitoring of persons, the surveillance of things, undercover agents and the controlled delivery and seizure of goods for confiscation purposes. This is because in the vast majority of these actions, in the judicial practice of criminal proceedings, there is evidence of excesses and even illegalities by the Judicial Police and the Prosecutor’s Office. To this end, the principle of judicial reserve and the new concept of the judge in criminal proceedings, as understood by the UN, will be studied: a procedural guarantee for weighing up conflicting rights. In this sense, it will be taken into account that in the Colombian constitutional state model, the limitation or restriction of fundamental guarantees must be proportional and reasonable in relation to the purpose of the investigation. Similarly, it is proposed, in the legislative sphere, the modification and creation of a single chapter on actions that require judicial authorisation to be carried out by the Attorney General’s Office. © 2024 Policia Nacional de Colombia. All rights reserved.