A mobile communications system according to an aspect of the present invention includes a control apparatus (100) arranged in a radio access network (20) and a policy supply system (200) arranged in a core network (10). The policy supply system (200) is configured to supply the control apparatus (100) with a first control policy used in control related to state transition of a mobile terminal (300) between a CONNECTED state and an IDLE state. The control apparatus (100) is configured to perform the control related to the state transition between the CONNECTED state and the IDLE state for the mobile terminal (300) based on the first control policy. This enables, for example, to reduce the number of signalings which are caused due to repetition of state transition (CONNECTED-IDLE transition) of the mobile terminal and are to be processed by the core network, based on the determination by the core network.