MADISON, Wisconsin - May 7, 2009 - Wisconsin police can attach GPS to cars to secretly track anybody's movements without obtaining search warrants, an appeals court ruled Thursday.

However, the District 4 Court of Appeals said it was "more than a little troubled" by that conclusion and asked Wisconsin lawmakers to regulate GPS use to protect against abuse by police and private individuals.

As the law currently stands, the court said police can mount GPS on cars to track people without violating their constitutional rights - even if the drivers aren't suspects.

Officers do not need to get warrants beforehand because GPS tracking does not involve a search or a seizure, Judge Paul Lundsten wrote for the unanimous three-judge panel based in Madison.

That means "police are seemingly free to secretly track anyone's public movements with a GPS device," he wrote.

One privacy advocate said the decision opened the door for greater government surveillance of citizens.

Meanwhile, law enforcement officials called the decision a victory for public safety because tracking devices are an increasingly important tool in investigating criminal behavior.

The ruling came in a 2003 case involving Michael Sveum, a Madison man who was under investigation for stalking. Police got a warrant to put a GPS on his car and secretly attached it while the vehicle was parked in Sveum's driveway. The device recorded his car's movements for five weeks before police retrieved it and downloaded the information.