No need to outlaw the device.

If the cop used an unauthorized GPS tracker without a warrant, you could take them to court for a Fourth Amendment violation and stand a pretty good chance at winning.

Even if you want to argue it was done purely as a personal citizen vs. citizen matter, you could almost certainly win a lawsuit for harassment and stalking.

There's plenty of precedent for both types of cases.

Flock cameras are stalking at scale, and they should not be tolerated.

I think even the most ardent supporter of CCTV or Flock or whatever would agree that misuse should be treated harshly. Zero difference between Flock and any number of investigative powers afforded to the government, many without a warrant. Misuse by an officer should be very heavily punished.