Thurgood Marshall's dissent in Smith v. Maryland (1979).

[JDPriestly]

3. It may belong to the phone company, but the government has no right to see it

if in looking at it and analyzing it, it violates my constitutional rights.

The decision in Smith v. Maryland was based on facts far too different from the surveillance that is going on today. Smith v. Maryland really did not implicate First Amendment issues. But the surveillance or potential surveillance of pen registers of journalists or members of Congress or the judiciary and their aides implicates all kinds of constitutional violations.