PRS (Public Regulated Service) is designed to provide position and timing to specific and authorized users requiring a high continuity of service using encrypted data. Typical PRS user will be organizations involved in public safety and security (police, fire fighters, health services, coast guards, etc.).
Open Service low signal power makes it vulnerable to unintentional or malicious interference (jamming). Under a scenario of several low-power jammers, PRS will also maintain service availability in this area affected by interferences. To affect PRS service it is required a high-power jammer, being this equipment more expensive and easier to detect.
Another undesired scenario might be the hostile use of open GNSS service by terrorists, criminals, etc. In this case the authorities will voluntarily interrupt open GNSS service to prevent its hostile use in situation where intelligence sources report a high threat of attack. In this case, the service will not be interrupted for the PRS users in the denied area, as they are registered as authorized users by their own government.