You have to broadcast a malicious signal (noise) strong enough to overpower the existing gps signals, which wouldn’t be that difficult to do as gps signals are weak and come from far away.

But it’s super duper illegal and would be trivial for local coppers or military to find you and wreck your world as you would be broadcasting a strong signal that clearly indicates your location.

So yeah, I do think most of what prevents people from doing this kind of thing more is just the fact that your local police/military will fuck you up for doing it and it will be real obvious to anyone near you who did the thing. They really don’t like people messing with their gps.