Thank you Ben for that excellent essay on Just War Theory and voluntaryism. Murray Rothbard wrote a piece on libertarian theory of war that I’d like to add to your argument. An excerpt:
The fundamental axiom of libertarian theory is that no one may threaten or commit violence (“aggress”) against another man’s person or property. Violence may be employed only against the man who commits such violence; that is, only defensively against the aggressive violence of another. In short, no violence may be employed against a nonaggressor. Here is the fundamental rule from which can be deduced the entire corpus of libertarian theory.
Let us set aside the more complex problem of the State for a while and consider simply relations between “private” individuals. Jones finds that he or his property is being invaded, aggressed against, by Smith. It is legitimate for Jones, as we have seen, to repel this invasion by defensive violence of his own. But now we come to a more knotty question: Is it within the right of Jones to commit violence against innocent third parties as a corollary to his legitimate defense against Smith? To the libertarian, the answer must be clearly no.