A little background is in order that the opinion is less than clear about. The case took place in the Gilded Age, when labor violence was at an all-time high in this country. Powerful companies hired the Pinkerton Detectives and other private goons as their de facto private armies. Unions countered them by raising their own armed forces, in this case, with the Socialist Labor Party. For this Presser, the head of the armed company, was charged with violating an Illinois statute forbidding military organizations other than those authorized by the state. As a defense, Presser argued that the statute violated his Second Amendment right to keep and bear arms. (Unsurprisingly, no such charges were brought against armed forces for powerful companies).
The Supreme Court decision is in some ways deeply offensive to our present-day understanding of the Constitution, but in other ways still current. It took the view current at the time distinguishing between the rights of "citizens of the United States," which were protected by the Fourteenth Amendment, and citizens of a state. In particular, most of the Bill of Rights was held to be a restriction only on the Federal Government and not the states:
The provision in the Second Amendment to the Constitution, that "The right of the people to keep and bear arms shall not be infringed" is a limitation only on the power of Congress and the national government, and not of the states. But in view of the fact that all citizens capable of bearing arms constitute the reserved military force of the national government as well as in view of its general powers, the states cannot prohibit the people from keeping and bearing arms so as to deprive the United States of their rightful resource for maintaining the public security.
The provision in the Fourteenth Amendment to the Constitution that "No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States" does not prevent a state from passing such laws to regulate the privileges and immunities of its own citizens as do not abridge their privileges and immunities as citizens of the United States.In this it cited the odious case of US v. Cruikshank, a case that deserves to live in the same infamy as Dred Scott and Plessy v. Ferguson, holding, in effect, that armed vigilantes in the South could deprive black people of their rights to their hearts' content, and the Federal Government could not intervene. But one can condemn Presser for citing Cruikshank and still regard it as sound in other ways.
Presser also avoided addressing the issue of whether the Illinois Military Code was in violation of Article I, Section 10, Clause 3 of the US Constitution, forbidding states from keeping troops other than the militia authorized by Article I, Section 8, Clauses 15 and 16. But it did make clear that states could ban private armies, and its basic reasoning is sound, even if it was unjustly applied in this particular instance:
Military organization and military drill and parade under arms are subjects especially under the control of the government of every country. They cannot be claimed as a right independent of law. Under our political system, they are subject to the regulation and control of the state and federal governments, acting in due regard to their respective prerogatives and powers. . . . The exercise of this power by the states is necessary to the public peace, safety, and good order. To deny the power would be to deny the right of the state to disperse assemblages organized for sedition and treason, and the right to suppress armed mobs bent on riot and rapine.And though we may be appalled at the narrow reading of the Bill of Rights at the time, that applied it only to the Federal Government and not the states, and although we may be offended that the double standard here, enforcing the ban on private armies only against labor and not against management, let us concede the opinion a point here that remains just as valid to this day. Military organization and drill and parade under arms are, or at least should be, subjects especially under the control of the government in every country. To allow unchecked proliferation of private armies is, indeed, an invitation to anarchy.
And the unequal way in which the ban on private armies was enforced raises another question that applies to the Patriot movement to this day, and that I plan to address in the near future -- if the Second Amendment guarantees a right to private armies and armed rebellion, just who is guaranteed that right.