This is probably the loophole by which both statements "cash is legal tender for all debts" and "not accepting cash is legal" can coexist. There is no debt if t

This is probably the loophole by which both statements "cash is legal tender for all debts" and "not accepting cash is legal" can coexist. There is no debt if the transaction does not happen because one of the participants is unwilling to enter it for some reason (with the reason being that the other person does want to pay cash). Banning specific reasons for not making business is possible however (it is done to protect ethnic minorities for example), so the situation can probably easily be changed by legislation that bans "wants to pay in cash" as a legit reason for not entering into a transaction at stores that are open to the general public.