Invoking the Patriot Act and other surveillance laws, Federal law enforcement has tried to track the location of cell phones without providing any evidence of criminal activity. The Justice Department’s surveillance requests were denied. Cell phones constantly broadcast their location even when no call is in progress. The FBI and other police agencies often seek access to that location-tracking information, which can reveal the cell phone owner’s movements. But only in the last few months have judges begun to scrutinize what have traditionally been routine tracking requests and concluding that police must show at least some evidence of actual criminal activity.