[mike_d]

> The United States do not have the ability to degrade or deny a gps signal based on location

This was a feature designed into GPS from the beginning. They just stop transmitting the C/A code from satellites visible to the battlespace and a device can't bootstrap or maintain a location fix. Approved devices entering the battlespace (say a ballistic missile fired from a ship over the horizon) can continue to maintain high precision location using the P code.

Block III sattelites have also started transmitting M code, which is a second generation of military only GPS that claims to be unjammable and unspoofable.