Re: EU friends apparantly @ ArrZarr
"You clearly don't seem to understand how GPS works".
Yes they can reduce the accuracy and even push a fake almanac and ephemeris data (I do know quite a bit about how they work) but that impacts all users in the region receiving that civilian signal. (Note, the military one is encrypted and different). But by knobeling the civilian signal they do it for all users except their own military. e.g if the Americans played with GPS to affect the UK it would also affect an American Airlines jet landing in Paris.
What situation are you expecting to be in when the Americans, Russians and Chines are all united in hurting themselves to do us harm?