Ces personnes peuvent toutes à un moment donné être en contact avec les autorités administratives de l'État où elles séjournent: les touristes avec le système de santé, les étudiants avec les services administratifs des universités, les travailleuses et les travailleurs avec les autorités fiscales et la sécurité sociale, etc.
In 2011, Eurostat estimated that some 12 million EU citizens were living in a Member State which was not their home country. Many more reside temporarily in another EU State, for example for purposes of study or work, or simply to take a holiday. All these people may potentially at some point come into contact with the administrative authorities of the country they are visiting or residing in – tourists with the health system, students with a university administration, workers with the tax and social insurance authorities, etc.