But the U.S. Congress and most states have not kept up with the times , Alito said , leaving courts to sort out what level of privacy a citizen can expect . Following a warrant for surveillance via a tracking device requires a search warrant , they say . The justices are divided on what they say makes the action unconstitutional . Justice Alito , for the majority , cites the ` ` physical intrusion '' of using the device . Four others say the lengthy monitoring violated the suspect 's expectation of privacy .
Following a warrant for surveillance via a tracking device requires a search warrant , they say . The justices are divided on what they say makes the action unconstitutional . Justice Alito , for the majority , cites the ` ` physical intrusion '' of using the device . Four others say the lengthy monitoring violated the suspect 's expectation of privacy .