It's harder to jam Starlink than GPS because the signals are directional, but if a government doesn't want you using it, they can just make the dishes illegal and throw you in prison for having one.

Starlink is under USA jusrisdiction, as far as I know. I'm pretty sure there's no concept of "international waters" for communication satellites.

AFAIK Most of the traffic goes: subscriber <-> (single) satellite <-> local base station. And the latter operates under the rules of given country.