Abstract: For their full operational capability, the European Union (EU) Global Navigation Satellite Systems, Galileo and EGNOS, have to rely upon Ground Sensor Stations (GSS) for the monitoring of navigation signals received from satellites and for the transmission of data to Galileo Control Centres through public networks. Some of the GSS will be installed in non-EU countries. Naturally, for these stations, the EU would like to maintain, inter alia, the inviolability of the premises: facilities free from all types of radio interference, hacking and eavesdropping attempts; the right to use codes; the privileges accorded to diplomatic personnel, communications and documents. The legal analysis of this problem has been based on the applicability of the 1945 United Nations (UN) General Convention on the Privileges and Immunities, the 2004 UN Convention on Jurisdictional Immunities of States and the 1961 Vienna Convention on Diplomatic Relations, as well as on international customary law. Consideration has been given to the legal personality of the EU, to the nature of the activities performed by GSS in order to assess EU immunity from jurisdiction or immunity from execution.