For at least a few years, courts throughout the country had disagreed on the following issue: whether the police should have to get a warrant in order to access cellphone data showing where someone has been. In June 2018, though, the U.S. Supreme Court settled the matter. It held that, in a typical case, the government needs a warrant to get cell-site location information (CSLI) from the relevant user's cellphone provider.
For more, read about the rule established by the case of Carpenter v. U.S.
Effective date: June 22, 2018