The 2nd Amendment "militia" is a conceptual framework, that can only be understood in the context of 1791. Don't worry about trying to apply it to today's realities.
The 1791 militia was the whole body of the people (or at least the white, free, male, able-bodied ones). Thus, the whole populace was supposed to hold itself in readiness for military service, equipped with its own arms and led by officers appointed by the state. There were annual musters to verify that the militia, in fact, was ready for service. This whole system fell into disuse by the time of the War of 1812. It never could work on a practical basis. It was mainly just an idea in the Founders' heads.
In today's terms, the 2nd Amendment "militia" is, simply, everybody. It's not the National Guard or various private self-appointed militias, all of which lack the essential element of universality. A select, self-organized "militia" does not qualify as a 2nd Amendment "militia." Such a "militia," by its nature, must remain unorganized.
If we take this analysis to its logical conclusion, the 2nd Amendment means that everybody is entitled to keep the same military weapons supplied to the standing army, including machine guns, mortars, artillery, etc. The courts, being instruments of "law and order," would never agree to such a radical interpretation, but it's the one the Founders left us with.