I have been watching starlink with interest. Don't have it, don't know when I will, but it sure would have been nice last year in the St Lawrence and the south coast of Newfoundland! So I have been following it with mild interest.
Seems to me that there are two ways to geofence. One is simply hardware
limitations, the way XM / Sirius geofence their service
to North america. You just can't get the signal way offshore. If starlink simply limits the service
to those areas that are served by a terrestrial station, the vast majority of cruisers will find it just dandy. Just don't allow connection on a relay station, super simple.
The far more rigorous, but slightly more technically challenging, would be to draw a bright red line 100 yards off the coast all the way around North America. Then plot your GPS
coordinates and if you are outside that line, present an error code.
The second would be a letter of the contract
implementation. But unless there are compelling reasons for him to do it, I suspect that he will go with the former. Sort of a position of "If it works, good for you - if it doesn't, upgrade your service."