39 C.F.R. § 3065.2 – Prohibition on new regulations.

(a) The Postal Service may not promulgate any new regulations or enter into agreements purporting to suspend or otherwise define the scope of the letter monopoly.
(b) The Postal Service may not promulgate any new regulations purporting to interpret 39 U.S.C. 601.
(c) The Commission has the sole authority to promulgate new regulations necessary to carry out 39 U.S.C. 601.