A controlled area (A) is configured as a telecommunications cellular system location area, connection of cellular system mobile terminals (T) to such location area (A) is checked. A detected connection indicates that the bearer of the terminal (T) accessed the controlled area, which information can thus be used both to prevent unauthorized access and to certify and document authorized access also by interrogation through the system. The fact that terminal (T) has been kept switched on inside the controlled area despite this being interdicted can also be detected and such behavior can be debited to the terminal (T) involved and/or the terminal can be inhibited by means of temporary deactivation of the terminal (T).