The publication is an outcome of a research concluded by the international group of authors on the question of how is the phenomenon of harmful interference faced by those operating space communication and broadcasting systems prevented and dealt with. It analyses the present regulatory system based on the legal instruments of the International Telecommunication Union (ITU), the involvement of national regulatory authorities in procedures dealing with harmful interference, and the role of the European Union in the integration of spectrum management. On the basis of examples of harmful interference, it concludes that the ITU is only partially equipped to deal with this problem: It lacks any own monitoring mechanism and the possibility of enforcement of its own decisions. However, the continuous effort to make the ITU mechanism more effective can be seen in the recent competence of the ITU RRB to cancel the frequency assignment with respect to specific satellite networks. The legal role of national administration in the procedures dealing with harmful interference is crucial; the question whether there should be a specific competence of the European Union in this area is still open.