This publication analyzes the justice system (prosecutorial and judicial) practice of approving, implementing and controlling SIMs. The analysis is based on the assumption that the various actors in this process face a number of challenges, each from their own perspective of procedural competence.

Among these is, of course, the challenge of balancing the general interest in safeguarding security against the interest of individuals in having their privacy respected. The generally accepted standard that the individual interest in privacy should be overridden only if it is assessed to be the only way to protect another high societal interest.

This places an obligation on the competent authorities in this process to respect the principle of proportionality and to propose and approve SIMs only if their implementation is necessary as a last resort, ultima ratio, in a specific case. This requires the application of the principle of subsidiarity or proportionality, that is, to start with the application of a less intrusive measure and proceed to a more intrusive one, and the implementation of the most intrusive measures should only be sought and permitted if the less intrusive ones do not yield the expected result.