The government cannot turn cell phones into tracking devices:

Federal law enforcement attempts to use cell phones as tracking devices were rebuked twice this month by lower court judges, who say the government cannot get real time tracking information on citizens without showing probable cause.

This summer, Department of Justice officials separately asked judges from Texas and Long Island, New York to sign off on orders to cellular phone service providers compelling them to turn over phone records and location information -- in real time -- on two different individuals.

Both judges rejected the location tracking portion of the request in harshly worded opinions, concluding investigators cannot turn cell phones into tracking devices by simply telling a judge the information is likely "relevant" to an investigation.

"When the government seeks to turn a mobile telephone into a means for contemporaneously tracking the movements of its user, the delicately balanced compromise that Congress has forged between effective law enforcement and individual privacy requires a showing of probable cause," wrote Magistrate Judge James Orenstein of New York in the latest decision Monday.

It seems reasonable to me that probable cause, as Judge Orenstein writes, should be a requirement before a governmental agency is allowed to track people via their cell phones.