On Monday, January 23, 2012, the U.S. Supreme Court ruled unanimously that the installation of a Global Positioning System (GPS) tracking device [Page 1087]on a vehicle without a warrant constitutes an unlawful search, which violates a citizen’s freedom from unreasonable searches and seizures protected under the Fourth Amendment to the U.S. Constitution. The Court, led by Chief Justice John Roberts, handed down this ruling as part of Justice Antonin Scalia’s majority opinion in the case the United States v. Jones. This entry reviews the background of the case and the lower court rulings before examining the Supreme Court’s rationale for its decision and the implications to future cases.