The chapter analyses, from a legal point of view, the conflict between the fundamental right to privacy of the employee and the exercise of managerial power by means of capturing images of employees by using CCTV and that of hiring detectives. The Spanish Constitutional Court admits that such means of control is legal provided that the measure used is justified, appropriate, necessary and balanced. However, the casuistic nature of the so-called “proportionality doctrine” allows the adoption of contradictory judicial solutions in analogous or identical cases, generating situations of legal uncertainty. This doctrine will have to be nuanced after the recent judgments of the ECHR in the cases of Barbulescu II and López Ribalda, resolutions that require a rethinking of the theory of fundamental rights of working people in Spain, within the framework of the new digital and technological era.