New submitter Blindman writes "The Sixth Circuit Court of Appeals has held that it is okay for police to track your cellphone signal without a warrant. Using information about the cell tower that a prepaid cell phone was connected to, the police were able to track a suspected drug smuggler. Apparently, keeping your cellphone on is authorization for the police to know where you are. According to the ruling (PDF), '[The defendant] did not have a reasonable expectation of privacy in the data emanating from his cell phone that showed its location.' Also, 'if a tool used to transport contraband gives off a signal that can be tracked for location, certainly the police can track the signal.'"