Back in January, a court in Portland, Oregon ruled that the Fourth Amendment rights of one Juan Pineda-Moreno had not been violated by the police when they tracked him using various GPS devices they installed on the underside of his Jeep with magnets. You see, the police suspected that Pineda-Moreno was growing Marijuana somewhere, and they really didn't like that. Eventually, Pineda-Moreno was arrested and convicted of crimes involving the growth of said Marijuana -- but he appealed the decision because he thought that his Fourth Amendment rights (the one which guards against unreasonable search and seizure) had been violated. The appeals court has recently upheld the original decision, but there were five dissenting votes, meaning that the case is anything but cut and dried. Now, what's obvious is that the police didn't have to traverse into "private" space to attach the tracking device to the suspect's car, but clearly it's debatable -- even as far as the judges are concerned -- what constitutes private and public space. The case is surely not going to end here, so we'll keep you updated. In the meantime, watch your back. [/p] Source They're allowed to do that without a warrant. Sucks for Americans. You can also do the opposite and put a GPS on a cop car, instead.