Professor Philip Zelikow explains that private armies are not legal in Virginia, via Lawfare:
The Second Amendment arguments can be—and have been—overcome. Individuals may have a right to bear arms for self-defense, but they do not have a right to organize and train as a private military group. In 1886 the Supreme Court laid the groundwork for controlling what the Second Amendment calls a “well-regulated Militia,” when it held that “[m]ilitary operations and military drill are subjects especially under the control of the government of every country. They cannot be claimed as a right independent of law.” A New York appellate court noted in 1944: “The inherent potential danger of any organized private militia is obvious. Its existence would be sufficient, without more, to prevent a democratic form of government, such as ours, from functioning freely, without coercion.” That language seems awfully resonant today.
The language of Virginia’s Constitution is clear. While “a well regulated militia” is valued, including what state law calls the “unorganized militia,” the Constitution stresses that, “in all cases the military should be under strict subordination to, and governed by, the civil power.”
Well, when truckloads of organized groups of heavily armed men drive into my town—or your town—it is time to uphold the civil power. Virginia, like most states, has the legal power to stop them. And the precedents are on the books.
This strikes me as one of those boundary cases found in systems. If you’re a revolutionary, this is one of those oppressive laws which puts you more under the thumb of the detested government. If you’re the government, this is a common-sense law which not only protects the government (a sentiment that falls apart under examination), but also criminalizes gangs that are sufficiently militaristic.
All that said, I have to wonder if Minnesota has such a law.