Criminals can legally be tracked without a warrant using a cellphone, an appeals court ruled on Aug. 14. Law enforcement did not place a tracking device, but rather used the GPS feature on a drug trafficker's cellphone to find and arrest him. The drug trafficker, named Melvin Skinner, appealed his conviction of two counts of drug trafficking and one count of conspiracy to commit money laundering on the basis that using his phone's GPS data without a warrant violates his Fourth Amendment rights.

The court justified the use of the phone's GPS feature by pointing out that police didn't place the GPS device, they simply made use of a feature that was already there. “The drug runners in this case used pay-as-you-go (and thus presumably more difficult to trace) cellphones to communicate during the cross-country shipment of drugs,” the court's opinion reads. “Unfortunately for the drug runners, the phones were trackable in a way they may not have suspected. The Constitution, however, does not protect their erroneous expectations regarding the undetectability of their modern tools.”

The U.S. Court of Appeals for the Sixth Circuit's decision runs counter to a Supreme Court ruling earlier this year stating that law enforcement cannot track a suspect's vehicle with GPS without a warrant. However, vague wording in that ruling, which is based on legislation from the 1970s, may allow for tracking by modern technology such as cellphones or computers. The Geolocation Privacy and Surveillance Act was introduced last year by Sen. Ron Wyden, D-Ore., and Rep. Jason Chaffetz, R-Utah, to update privacy law to include modern technologies and bring consistency to these rulings.