For about four weeks in 2005, Antoine Jones unsuspectingly drove around with a Global Positioning System tracking device attached to his Jeep. The device recorded the vehicle's every movement, 24 hours a day, seven days a week.

It tracked Jones to his northeast Washington, D.C., nightclub and to a residence in nearby Prince George's County known to law enforcement officers as a stash house. The tracking device, calibrated to capture the vehicle's position every 10 seconds, produced 3,000 pages of records that proved instrumental in convicting Jones on drug charges.

The conviction was overturned last year when the U.S. Court of Appeals for the D.C. Circuit ruled that the government breached the Constitution -- and Jones's reasonable expectations of privacy -- because law enforcement officers placed the device on the SUV and tracked his every movement without a valid court order.

The Supreme Court is scheduled to hear the case in its upcoming term. It's not an easy case, but we think the appeals court got it right.

The Justice Department argued in a recent brief that warrants aren't needed for such GPS tracking. After all, officers have been tailing suspects pretty much for as long as detectives have roamed the Earth, and in this country police have never needed court permission to do so.

But tailing someone doesn't require encroaching on private property, as does affixing a tracking device. The significant investment of personnel and time necessary to tail a suspect acts as a constraint.

And human surveillance is highly unlikely to yield the comprehensive results that are available through GPS, which can track a suspect automatically, relentlessly and at little expense.

GPS tracking of a targeted individual is also different from police or security cameras, which capture the fleeting movements of random individuals and vehicles that move through a particular space.

"A person who knows all of another's travels can deduce whether he is a weekly churchgoer, a heavy drinker, a regular at the gym, an unfaithful husband, an outpatient receiving medical treatment, an associate of particular individuals or political groups -- and not just one such fact about a person, but all such facts," D.C. Circuit Judge Douglas Ginsburg aptly noted in invalidating Jones's conviction.

GPS is a valuable tool, and the vast majority of law enforcement officers would probably use it appropriately. But there should be a check against what Judge Alex Kozinski of the California federal appeals court called the possibility of "creepy and un-American" government acts.

Requiring a court order before launching a lengthy and intrusive tracking project is not too much to ask.