— Murray N. Rothbard from ‘War, Peace, and the State.‘

Let us set aside the more complex problem of the State for awhile 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. Remember that the rule prohibiting violence against the persons or property of innocent men is absolute: it holds regardless of the subjective motives for the aggression. It is wrong and criminal to violate the property or person of another, even if one is a Robin Hood, or starving, or is doing it to save one’s relatives, or is defending oneself against a third man’s attack. We may understand and sympathize with the motives in many of these cases and extreme situations. We may later mitigate the guilt if the criminal comes to trial for punishment, but we cannot evade the judgment that this aggression is still a criminal act, and one which the victim has every right to repel, by violence if necessary. In short, A aggresses against B because C is threatening, or aggressing against, A. We may understand C’s “higher” culpability in this whole procedure; but we must still label this aggression as a criminal act which B has the right to repel by violence.

To be more concrete, if Jones finds that his property is being stolen by Smith, he has the right to repel him and try to catch him; but he has no right to repel him by bombing a building and murdering innocent people or to catch him by spraying machine gun fire into an innocent crowd. If he does this, he is as much (or more of) a criminal aggressor as Smith is.”