An FBI document explains how it gets tracking data from US phone companies.

The issue here is not whether phone companies should answer subpoenas. Rather, it is what data they accumulate.

To track everyone's movements this way is not merely unjust to each person tracked. It threatens good government by facilitating the identification of whistleblowers. It threatens democracy itself, by facilitating the identification of dissidents.

Therefore, I contend that phone companies should not be allowed to retain tracking information about any person without first receiving a specific court order.

As someone once told me, in what kind of state is the job of the police easy? In a police state.