Federal Reserve Notes are lawful to use. Thus the confusion.
Yet, FRN's shall be redeemed in Lawful Money on demand at any FRB.
Legal Tender vs. Lawful Money = Legal vs. Lawful
FRN's should not be considered "lawful money" otherwise why would they need to be redeemed for such? FRN's redeeming FRN's....?? I have a page on just that...will post when I get my scanner working