<prompt> Translate the following text to EnglishKama ilivyoelezwa katika taarifa ya Tume ya Ujumbe wa Marekani, Mfumo wa mkataba wa kisheria haupaswi kuwa na mipaka ya kisheria, lakini hakuna mpango kama huo utakaoruhusiwa bila ushiriki wa Tume kulingana na 39 USC.  <response>: The Postal Service commented that, in its view, legal constraints would not preclude a contract mechanism in principle, but that no such arrangement would be permissible without the Commissions participation in accordance with 39 U.S.C. 