"Defensive violence, therefore, must be confined to resisting invasive acts against person or property. But such invasion may include two corollaries to actual physical aggression: intimidation, or a direct threat of physical violence; and fraud, which involves the appropriation of someone else’s property without his consent, and is therefore “implicit theft.”
Thus, suppose someone approaches you on the street, whips out a gun, and demands your wallet. He might not have molested you physically during this encounter, but he has extracted money from you on the basis of a direct, overt threat that he would shoot you if you disobeyed his commands. He has used the threat of invasion to obtain your obedience to his commands, and this is equivalent to the invasion itself.
It is important to insist, however, that the threat of aggression be palpable, immediate, and direct; in short, that it be embodied in the initiation of an overt act. Any remote or indirect criterion – any “risk” or “threat” – is simply an excuse for invasive action by the supposed “defender” against the alleged “threat.” One of the major arguments, for example, for the prohibition of alcohol in the 1920s was that the imbibing of alcohol increased the likelihood of (unspecified) people committing various crimes; therefore, prohibition was held to be a “defensive” act in defense of person and property. In fact, of course, it was brutally invasive of the rights of person and property, of the right to buy, sell, and use alcoholic beverages.
In the same way, it could be held that
- the failure to ingest vitamins makes people more irritable, that
- the failure is therefore likely to increase crime, and that therefore
- everyone should be forced to take the proper amount of vitamins daily.
Once we bring in “threats” to person and property that are vague and future – i.e., are not overt and immediate – then all manner of tyranny becomes excusable. The only way to guard against such despotism is to keep the criterion of perceived invasion clear and immediate and overt. For, in the inevitable case of fuzzy or unclear actions, we must bend over backwards to require the threat of invasion to be direct and immediate, and therefore to allow people to do whatever they may be doing. In short, the burden of proof that the aggression has really begun must be on the person who employs the defensive violence." ~ Rothbard, Right to Self Defense.