To me, the interesting question would be, were a private citizen to build a tracking device and attach it to an FBI vehicle, would they have a problem with that

To me, the interesting question would be, were a private citizen to build a tracking device and attach it to an FBI vehicle, would they have a problem with that? My guess is they would arrest you and figure out something to charge you with -- even though, by their own logic, since you could follow an FBI vehicle around to see where it goes, attaching a GPS is equivalent. A logical standard would be "that which isn't legal for a private citizen to do, the police need a warrant for" -- but hey, I'm an engineer, not a lawyer...