not necessarily, i think. anarcho-capitalism implies that the non-aggression principle is optional because the enforcement of laws is open to competition. then again, using violence against competition is unlikely because of the very high cost, so disputes are most likely settled peacefully. point is: minimal state could be justified while still somewhat following the rules of libertarianism.
No, absolutely necessarily.
Consider the following:
According to libertarian philosophy, the only way to violate rights is by initiating force (committing aggression). If it wasn't obvious, defensive, restitutive, retaliatory, and punitive force is not an initiation of aggression, but force used in response to aggression.
In the case of the human body, aggression is invading the borders of someone's body (battery) or, more generally, using the body of another person without their consent.
Non-libertarian philosophies have a different view. Usually that means that each person has some limited right in their own body, but not complete or exclusive rights. Society or the state also have certain rights in each citizen's body.
The libertarian philosophy has the fundamental goal of avoiding conflict, and legitimizing the control of outsiders is just a way to create conflict. According to this point of view, non-libertarians who endorse anything less than a 100% exclusive self-ownership are basically maintaining that the state is at least a partial owner of the body of other people, or even a complete owner in the case of conscriptees or nonviolent "criminals" who are incarcerated.
Without property rights, there is always the possibility of conflict over contestable (scarce) resources. Unless there is some pre-established harmony of interests, you and I cannot do different things with a thing (= the thing is scarce) without getting into a physical conflict with one another. By assigning an (exclusive) owner to each resource and establishing visible boundaries that non-owners can avoid, a libertarian legal system makes a conflict-free use of resources possible. And when it comes to the rule of property assignment, self-ownership is favored over other-ownership (slavery).
I hope I don't need to elaborate more on self-ownership, but if you need me to, that's fine.
External objects (things, goods) are not directly controlled by your own will, and they are initially unowned (given by nature). The libertarian establishes an objective link by means of appropriation (transforming, embordering, homesteading, possessing a previously unowned resource). Also, the first/prior user of a previously unowned thing has, prima facie, a better claim than a second/later claimant, solely by virtue of being earlier. Again, the goal is conflict-free use of resources. The answer to "who is the owner?" can't be "whoever has the thing or whoever is able to take it", because that boils down to a might is right system which makes conflict inevitable.
Again, I hope I don't need to elaborate on the libertarian concept of ownership in external things, but again, if you need me to, I will.
Now, the state is necessarily an aggressor and thus in violation of the most basic of libertarian ideas.
Thus, everybody who is not an anarchist must maintain at least one of
(a) aggression is justified
(b) states do not necessarily employ aggression.
(b) is plainly false as taxation is a form of aggression. Prohibiting competing defense agencies, which states also do, is also aggression.
(a), socialists and criminals also feel that aggression is justified. But that doesn't make it so. Criminals, socialists, and archists have yet to show how the initiation of force against innocent victims is justified, and it is not possible to show this.
