Speaking on Deep Background, the Press Secretary whispered:
Two relevant points on GPS/LORAN
1 - GPS has two positioning systems
1 - SPS Standard Positioning Service which is what all civillian
uses of GPS utilize for positioning and timing uses and this can
be degraded or disabled with no notice to the user community
by the National Command Authority.
I do not believe this is still true. To get ICAO approval for
using GPS as a intl. standard; DoD had to sign a MOU to maintain
the service.
They did this because they figured how easy it was to jam locally,
vs take down an entire region.