I have an idea that might just work. It would be legal and might even reduce the taxes participants would need to pay.
The U.S. Mint does put out gold and silver coins that ARE legal tender. These are normally sold as bullion because the $ amount stamped on them is far less than the actual value of the gold or silver.
So here is my idea: A business could, in theory, offer a “discount” to customers who pay in this type of “legal currency”. The business owner could even pay far less in taxes for that transaction because as far the the government is concerned the transaction was in U.S. Currency and not in gold or silver. This kills two birds with one stone. How could the federal government object? The transaction was made in currency that has their legal stamp of approval. The business owner is simply providing a discount to some customers who pay in a certain TYPE of legal U.S. Currency.
Ryan