Secrecy of correspondence

Paper letters have, in most jurisdictions, remained outside the legal scope of law enforcement surveillance, even in cases of "reasonable searches and seizures".

The secrecy of letters and correspondence is derived through litigation from the Fourth Amendment to the United States Constitution.

[9] In an 1877 case, the U.S. Supreme Court stated: No law of Congress can place in the hands of officials connected with the Postal Service any authority to invade the secrecy of letters and such sealed packages in the mail; and all regulations adopted as to mail matter of this kind must be in subordination to the great principle embodied in the fourth amendment of the Constitution.

[11] In the Supreme Court case California v. Greenwood, protections similar to those afforded to correspondence have even been argued to extend to the contents of trash cans outside one's house, although it turned out to be unsuccessful.

By Supreme Court precedent, rights derived from the Fourth Amendment are limited by the legal test of a "reasonable expectation of privacy".