On Thursday, May 10, 2018 at 5:14:49 PM UTC-7, wrote:
The US military built, owns, and controls it, but the user base has kind of gotten out of hand.

They might could turn it off any time they want once, but it might be a career limiting event.

If they caused a wide outage without a good reason, there would be a political backlash from the number of folks that paid for it being inconvenienced or worse.

The US military does not "own" GPS; the US Air Force operates it (it is owned by the US government). Selective Availability was ended in the 1990s by Bill Clinton. Since then, GPS has become a critical resource used by all government agencies, but, most importantly, by the FAA. GPS will only be shut down in the event of a critical national emergency; can you image the impact on airliners using a GPS IFR approach that suddenly went dark? For more info, go to:
https://www.gps.gov/systems/gps/performance/accuracy/

Tom