I opened a futures trading account at a futures brokerage that requires a $100 minimum deposit. Are these minimum deposits specified by any regulator, or is it up to each broker to set a minimum amount? If it is specified by regulations, could you provide a link to the rules?
Are these minimum deposits specified by any regulator
"no". The futures regulations contain the minimum required margin for a position. THIS does put in a minimum - if your account is lower than the lowest margin requirement, it can NEVER EVER open a position PER DEFINITION, but this has never been formalized into account requirements.
So, it is up to the brokers and I would stay seriously away from a broker that hunts for clients for accounts of 100 USD. This is comically low for anything to do with futures.