I know that someone 100 yrs ago in San Francisco “minted” their own money and people accepted it. I can’t think of the name, though
As I recall banks issued their own demand notes in the US not that long ago. As far as I know, private currency is not illegal. It might be considered a security - and require SEC registration.
Joshua Abraham Norton (c. 1819 – January 8, 1880). He declared himself Emperor of San Francisco, got a lot of free stuff from the locals.
We have had a number of private mints in the US throughout history but they were able to verify their metal content etc. Several states are considering minting their own coins as we speak. The GA legislature passed a bill that says you can pay any debt in the state of GA with gold or silver coins. I think competition is on the way.