Basically, if an American storekeeper says “I’ll only accept Mexican pesos, and don’t you dare try to pay with anything else.” what’s stopping him? Is he legally obligated to accept American dollars? What if he only wants to accept buckskins or dandylions? Or does the legal just mean, that’s what you pay taxes with and that’s what they tax?
BTW, I did use the example of an American, but I’m really Canadian and would appreciate to learn about any of the countries you would happen to know of.