4th amendment says (paraphrasing) "secure in their properties". if you're going to tell me that your car belongs to the public because it travels on public roads then your home should also be public because it sits on a public street. and the contents of your wallet are public because you have it with you in the store, which is a public place.

but, if you actually own your car (or lease for that matter), then law enforcement should not be able to track you indiscriminately just because your car goes on public streets to public places. it's still private property and should be protected by the constitution from electronic surveillance without a warrant. they used to need a warrant to listen to your phone calls -- although this could be granted retroactively because of FISA. why should they not need a warrant to place a device on your personal property so they can facilitate their tracking?

you're arguing that the feds (and now local police) can place a device on your car without your consent in order to track your movements, and to do so without judicial oversight, in order to collect data about your movements in the event you happen to commit a crime some time in the future, maybe. or you don't even have to actually commit a crime, you could just be in the wrong place at the wrong time, but now you're a suspect because of your tracking device. it would be like the police breaking into your house, finding something wrong, and being allowed to charge you for a crime without once ever going to get a warrant to search your house. and i'm not talking about hearing something suspicious coming from your house, i'm talking straight up just walk right in the door for no reason other than that they can. it should not be allowed without a judge issuing a warrant for the practice.