I've been mulling this one over for a while, but haven't researched it, so, yet again, I have no idea how original I am. I'm just putting my thoughts out there.
Everything in our social existence, including the operations of government, must be applications of what is right and wrong for individuals to do. Each individual must be able to identify what they are morally entitled to do and morally obliged to accept that others are morally entitled to do, at least in the first instance of such action. In regards to government, the anarchist is one who never gets past that final caveat, and says that there is only that "first instance" in all cases. They are not querying the use of voluntary mediation, for instance, but of the existence of the state, of a body embued with a monopoly on the non-emergency use of retaliatory force. It is that monopoly they reject, not the existence of a body as such. So, how does one respond to this without relying solely on mere pragmatic reference to separation of whim and force? How does one fully justify one's insistence for such a monopoly and even the right to enforce it upon others at the point of a gun?
After some thought I discovered that is actually quite simple in principle. Here's my thesis: if, when two parties A and B have a dispute, one can demonstrate that in at least some circumstances third party C is morally entitled to unilaterally intervene in that dispute and demand that it be settled in such-and-such reasonable fashion on pain of both A and B being subject to C's retaliation independently of the content of the dispute A and B have, and justify this unilateral intervention on the basis of C's own rational self-interests as an individual rather than reference to social good or whatnot, then as a matter of principle one has blown anarchism out of the water and has given the foundation of the State while retaining the principles of rationality, egoism and the inviolability of the rights of man all with their full force.
Reference to rights as the means to making society subject to the moral law, and of having a single body with a monopoly whose reason for being is so that the use of force is separated from the potential for individual whim, while entirely correct, comes after that. With that I leave you for now with two related questions: how does one make such a demonstration as a matter of principle, and, how does this translate into the State and all this entails? Have a think, and post a comment if you care to.