"United States Codes
Title 18 – Crimes and Criminal Procedure
Part 1 – Crimes
Chapter 83 – Postal Service

Section 1702
Obstruction of Correspondence

Whoever takes any letter, postal card, or package out of any post
office or any authorized depository for mail matter, or from any
letter or mail carrier, or which has been in any post office or
authorized depository, or in the custody of any letter or mail
carrier, before it has been delivered to the person to whom it was
directed, with design to obstruct the correspondence, or to pry into
the business or secrets of another, or opens, secretes, embezzles,
or destroys the same, shall be fined under this title or imprisoned
not more that five years, or both."