Announce that and within a week the airwaves of Spanish language stations will be filled with commercials offering to route remittances through Canada or the Bahamas or Jamaica or some such place. For a nominal fee, of course. Within two weeks remittances to Mexico will be near zero.
We could outlaw such a thing with a stroke of a pen. Now what? Abuela needs her money she’s depending on.
Simple response to such a scenario. Tax all remittances.
Germany adds a value added tax and reimburses those that leave its borders.