A "well regulated militia", back when, our constitution was written meant every able bodied and armed man who was not in the Army whose help could be requested in a time of danger.
When the Constitution was ratified, the Framers unanimously believed that the "militia" included all of the people capable of bearing arms.
"well regulated" … the term meant only what it says, that the necessary militia is well regulated (trained), but not commanded by the national, state, or local government.