Libertarians believe, as Murray Rothbard put it, that all rights are property rights.
Thus, “life” and “liberty” would fall under the category of “property.” I.e. You have a metaphorical right to “life” because your body is your property.
As Ludwig von Mises pointed out, every action is undertaken to substitute a more satisfactory state of affairs for a less satisfactory state of affairs. And, as Henry Hazlitt extrapolated, this implies that the singular, ultimate desired end of all acting humans is the long-run maximization of personal satisfaction.
Ethics is a system of recommendations for action (oughts) that apply to all acting humans. However, oughts merely connect desired ends with the means most appropriate to achieve them. I.e. “If you desire to bake a cake (desired end), you ought to buy some flour (means most appropriate)”
Thus, in order for there to be “oughts” that apply to all acting humans, all acting humans must share one universal desired end in common, which they do: long-run maximization of personal satisfaction.
However, as Hazlitt also pointed out, actors cannot judge all the infinite and unforseeable effects of any given action considered in isolation, and thus cannot know whether any particular action will actually lend itself to a net maximization of long-run personal satisfaction or not. But, we can follow the logic of human action and recognize correct general rules for action.
The first ethical issue one must resolve is, how ought individuals act in regard to selves? A general rule needs to be recognized regarding selves A). because your self is scarce and thus conflict is possible between you and another person over it, and B). because if, as a general rule, you ought not be allowed ultimate jurisdiction over your self (i.e. ownership over your self), then you have no basis to undertake any further action using your self.
As Rothbard pointed out, there are only three possible options. Either:
A). You own your self.
B). Some other person or group of people other than you, owns you.
C). Everyone has an equal share of co-ownership in everyone else.
Option B fails straightaway, simply because it is not a general rule applicable to all acting humans, but is rather a specific rule, arbitrarily applicable in one way to some humans, and in another way to other hunmans.
Option C would necessitate that in order for you to undertake any action with your self, you would have to obtain the consent of all other co-owners of your self. But the action of seeking their consent would itself need their consent. Thus Option C would ethically paralyze all further action. Option C is not a functional ethic.
Only Option A (you are your own property) is a functional ethic. The Principle of Self-Ownership is the most appropriate general rule/ethic (means) to employ to obtain long-run maximization of individual satisfaction (desired end).
If you own your self, you necessarily own your actions. If you own your actions, you necessarily own your labor (the fusing of your active efforts with untapped natural resources). And if you own your labor, you necessarily own the fruit of your labor (the property you come to acquire).
The fact that the system of private property is the most appropriate ethic to employ in regards to scarce resources in this world can be proved by examining all the alternatives. Here, again, there’s only 3 options:
A). The first person to appropriate and use a resource is its rightful owner.
B). One person or group of people owns all resources, and others don’t.
C). All users of a resource (which would mean users past, present, and future) equally co-own all resources.
As before, Option B fails straightaway as it is not actually a general rule.
Option C fails because you would somehow have to get the consent of future users of the resource (late-comers) before you could use any given resource. It would basically ethically paralyze all action with any resource other than your self. Option C is not a functional ethic. It is a grossly inappropriate general rule to employ as a means in the pursuit of the ultimate desired end.
Only Option A (that the first person to appropriate and use a scarce resource becomes its owner) is a functional/appropriate ethic.
If you are the owner of some thing, it may be said that you have a just claim to that thing. A metaphorical concept to describe a “just claim” to something, is a “title.” Using the word “title” simply makes it easier to conceptualize ownership.
If you have an ownership title in something, then you may, of course, dispose of it or transfer it as you will, so long as you do not violate the physical integrity of anyone else’s property. There is certain property, however, that you cannot possibly dispose of or transfer, such as your self or your will. You may pretend to transfer the title to your self to someone else, but in actuality, you necessarily always remain in [both physical and ethical] ultimate jurisdiction (ownership) over it. Thus, for example, libertarians generally see slavery as an illegitimate and ethically unenforceable faux contract.
The Non-Aggression Axiom is basically a nice, neat name to describe the fact that no one may violate (i.e. aggress against) any one else’s property. Person A may not act toward Person B’s property in a physical way in which Person A implicitly presumes a higher authority over Person B’s property than Person B has himself. If you own something, then what happens to that something ought to be subject to your ultimate decision-making, overriding the decision of everyone else concerning that something. If anyone acts in violation of this ethic, they are committing “aggression.” “Illegitimate” merely means that something goes against what is “ethical,” and of course what is “ethical” merely means action that is line with the general rules that are the most appropriate means to employ in pursuit of long-run maximization of personal satisfaction, given the fact that scarcity exists and thus interpersonal conflict is possible.
“Implied aggression” is only wrong if your act of implying the future use of aggression against someone is done so in an attempt to exercise a presumed higher claim over someone else’s property than that someone has over their own property. In this sense, “implied aggression” or “threatening aggression” is really an aggressive act in and of itself.
Hope this helps.