This is far from a new thing. In 1979 the Supreme Court decided (Smith v. Maryland) that pen registers and tap and trace devices did not require a warrant. The basis is that you have no expectation of privacy because a reasonable person knows that the phone company itself is privilege to details such as calling party, receiving party, time, and duration.
The 2001 PATRIOT ACT clarified the Pen Register Act, extending this privilege to internet communications.
The 2001 PATRIOT ACT clarified the Pen Register Act, extending this privilege to internet communications.