It would be a US law so they can get their money back in foreign currencies since its cryptographic and can be transferred to other exchanges internationally, and if they want dollars they can exchange it on the open market. Thankfully, that would increase the demand for dollars and continue to strengthen a currency weakened by a massive speculative market primed through international drug trafficking.
I see I read exchanges not as "marketplaces" but as "transfers of crypto in exchange for money" like you were going to have the government forcibly compel everyone in the US holding crypto to sell it for a flat USD value and thusly divest themselves. So your idea would be that they can keep holding crypto or they can sell it for otherd-than-USD-fiat in non-US exchanges. Makes sense.
