We already have it to some degree, it's not easy to own foreign currency in the US and for the most part it must be bought in the form of "futures." Foreign ban

We already have it to some degree, it's not easy to own foreign currency in the US and for the most part it must be bought in the form of "futures." Foreign banks have special reporting requirements for US citizens and many foreign banks will absolutely not take US money without large minimum balances or a local job.