39 U.S.C. § 1009
An officer or employee of the Postal Service may not receive any fee or perquisite from a patron of the Postal Service on account of the duties performed by virtue of his appointment, except as authorized by law.
(Pub. L. 91–375, , 84 Stat. 733.)
Section effective , pursuant to Resolution No. 71–9 of the Board of Governors. See section 15(a) of Pub. L. 91–375, set out as a note preceding section 101 of this title.