If a police car is on a public highway, I can follow it. Therefore, I can secretly place a GPS transceiver on the police car, and track its movements wherever I want. Do I understand this ruling correctly?
How about the car of that cute girl down the street?
Wasn't a guy charged with stalking last year because he secretly placed a GPS tracking unit in her car so he could follow her movements? This guy should get a new trial after this ruling - the girl had no expectation of privacy.