I bet half of houses in my neighborhood has a TV dish. If it will be possible to make Starlink dishes visually indistinguishable from those, the police will have a slightly harder time. Slightly, because detecting radio transmission doesn't seem hard either.
Transmissions from ground to orbit tend to be highly directional (it's why satellite TV/internet typically uses dishes instead of ordinary antennae). Detection from the ground would be pretty difficult, given that most (ideally all, but there's probably at least some leakage) of the signal will never reach anything else on the ground (for the same reason you typically can't see the beam of light from a flashlight or laser pointer unless it reflects off dust or fog or some other particulate in the air).
The most reliable way to detect ground-to-space transmitters would be with aircraft, since those will have a much easier time crossing paths with the signal (and thus actually being able to see it).
Hint: Not very.
Also, how exactly do you plan to pay your bills to your ISP, when their service is illegal in your country?