> the US government has laws against using gold as currency

I don't think that's true, or I can't find any evidence of it. If you want to buy a car and the seller agrees to accept 50 gold coins instead of $100,000 cash, that is perfectly legal. Hell, the US makes currency out of pure gold that are currency at face values of $5-50 (but the gold in the coins is worth 100x more than the face value).

Are you talking about the Gold Reserve Act of 1934 and Executive Order 6102? That banned private ownership of gold and demanded that citizens turn in their gold. But it was lifted in 1974.