The Third Circuit case involved a crime ring targeting Rite Aid pharmacies. The FBI used a"'slap-on" GPS tracking device to follow electrician Harry Katzin, who was suspected of cutting the stores' alarms before each heist. Ars Technica reported that while the FBI had the permission of the United States Attorney, they did not have a warrant. Katzin and two of his brothers where later arrested and charged with the robberies using evidence gathered via the tracking devices. This recent ruling means the primary evidence against the Katzin brothers will be inadmissible in court.
The Supreme Court ruled in the 2012 case of The United States v. Jones that such practices were unconstitutional, however that ruling didn't address whether a lower legal standard than probable cause could apply. In 2008 Antoine Jones was convicted of operating a cocaine ring based on evidence gathered via a GPS device that police placed on his Jeep. Evidence gathered by the device was thrown out of court and his conviction overturned. After three trials, Jones accepted a plea deal for 15 years with credit for time served.
The Third Circuit Court ruled that such devices fly in the face of the protections afforded citizens by the Fourth Amendment. Katzin and his accomplices will have the evidence against them thrown out of court. The American Civil Liberties Union and the Electronic Frontier Foundation both released statements applauding the ruling.