NYTimes: Justice Dept. to Require Warrants for Some Cellphone Tracking by Nicholas Fandos:
The Justice Department will regularly require federal agents to seek warrants before using secretive equipment that can locate and track cellphones, the agency announced Thursday, the first regulations on an increasingly controversial technology. The new policy, which also limits what information may be collected and how long it can be stored, puts a measure of judicial oversight on a technology that was designed to hunt terrorists overseas but has become a popular tool among federal agents and local police officers for fighting crime.
DOJ Policy Guidance document is available here.