The purpose of this research was to examine the system of legal protection when using so called secret coercive measures, i.e. telecommunications surveillance. The coercive measures are regulated in the Coercive Measures Act entered into force in 1987. Since then the legislation has been amended several times and is therefore considered very inconsistent. To clarify the legislation the preparations for a thorough revision of the Pre-trial Investigation Act, Coercive Measures Act and the Police Act were started in 2006.

In the first part of the research are determined the coercive and secret coercive measures and the legal remedies available according to the existing legislation. In the second part of the study I concentrate on finding out the changes proposed to the Coercive Measures Act by the committee working on reform to legislation on criminal investigations, coercive measures and police activities.

The information for this study was gathered mainly from legal literature and written law including the legislative materials. One of the most important sources was the white paper of the committee, which included their proposal for the new Coercive Measures Act.

As a result of this thesis it is easy to make the conclusion that if all the changes suggested by the committee will be approved, the legislation will get much more consistent and easier to apply. At the same time the fundamental rights and legal safety of the targets of coercive measures will be better guaranteed.