The Federal government decided that having a broadcast positioning system may pose some sort of threat to national security. When the time is downloaded by a receiver it will calculate a range to the satellite and be off by up to 100m horizontally and 200m vertically. The government can get around this introduced error by using special receivers not available to the general market.
Civilians can get around the problem just as easily by having two receivers.
One receiver sets up on a known position. Then it can be downloaded to compare with another receiver's recorded data, or it can be set to transmit the clock correction immediately to the other receiver.