OK... here is the excerpt:
It is also to be noted that Congress Has already come to grips with the question whether United States notes are legal tender in 31 U.S.C. s 452, which provides:
United States notes shall be lawful money, and a legal tender in payment of all debts, public and private, within the United States, except for duties on imports and interest on the public debt.
Thanks David!
Dioug