Interference occurs when unwanted emission occurs in frequency bands used for receiving low-level signals.
In the X-band, for example, the frequency band of 9.0- 9.8 GHz is reserved for radio location, therefore most radars operAte there. One section, 10.00 to 10.25 GHz is reserved for radio-amateur communication, and certain other services like industrial sensors operate there.
For satellite communication, 10.7 to 12.7 GHz is reserved for down-link communication, and no other service is allowed there.
If an interference occurs, it means the operator failed to meet the regulations (or some emitters are intentional), and state frequency agency is authorised to prosecute such illegal emission.
In general, interference can be mitigated by using larger antennas or interferometers that can reduce the signals coming from certain directions, using screens, sometimes filters and in terrestrial links by redesigning the technical parameters to counter stray signals.
Licensing frequencies and patrolling their use is a task for state agencies which receive money from licensing and taxes. Users are directed by law to use their systems carefully and not to cause interference to other users.