I was correcting myself after the light went on. You're way ahead of me, and most others, on this. Kudos for posting the law. There is one issue I see. That is trying to use various substances (gold, silver, copper, ...) for the same denominations.
I don't see an issue using various substances as money, just trying to use them for some arbitrary denomination creates a problem with value. The value of multiple elements will vary in a free market environment.
Instead of establishing a national denomination, i.e., the dollar, the yuan, the pound, let us use mass by element. Say 1 ounce or 28.35 grams of gold eagles/silver eagles (in the US), etc. Other countries could call them Maple Leaves, as long as we use common masses and purity - grams probably.
Further, markets must set the value of the elements, not government or the money changers.
Anything other than physical will need a third-party trust arrangement. Governments prove through history to be utterly unreliable after a while. Eventually even hiding what they have on hand from their people.
When you can schedule our first meeting with the world's leaders, let me know so that we may begin to revamp the world's monetary system! :)
Nobody is saying it will be an easy solution.
Easy and simple aren't synonymous.