You can literally see the packets of data that the receiver receives. You, me, the guy who runs Mamnick, anybody who owns a receiver and a computer, can see the data.
So unless each receiver is filtering out confidential information, which means every single device manufacturer is in on the system, that's just not possible.
If the GPS signal from the x number of sattelites that you have a fix with says "civilian_active=false" (or code to that effect) then your receiver will not work.
Anyway, it really doesn't matter, because it is vanishingly unlikely that this is done by country code.
You can literally see the packets of data that the receiver receives. You, me, the guy who runs Mamnick, anybody who owns a receiver and a computer, can see the data.
So unless each receiver is filtering out confidential information, which means every single device manufacturer is in on the system, that's just not possible.