GPS is funded by and controlled by the U. S. Department of Defense
(DOD). While there are many thousands of civil users of GPS world-wide,
the system was designed for and is operated by the U. S. military.

IIRC, President Clinton decreed that the GPS system be made available
for public use. But that was not its original purpose, nor is it now
its first priority. If the DOD wants to take it off line for testing,
that's their prerogative.