You are talking about private militia.
Most are prohibited from public functioning by state law.
As a rule militia callups are conducted by county sheriffs at the order of the governor.
They report to the sheriff as volunteers and are deputized under color of state authority.
They can leave at any time or be drafted.
A state Guard unit can be as few as a regiment.
A mere county sheriff can have a regiment of volunteer militia report - the numbers of a state militia can be vast.
Thanks for he information. I did not know that.