A woman hired somebody to mow her lawn. The hired person accidentally hurts himself very badly with the lawn mower. The woman, under the influence of a powerful hallucinogenic drug, gets out of the house and just watches the man from a relative distance as he is suffering. The contract between the two did not stipulate anything about such a situation. However, a neighbor observes the suffering man and tries to come to his help. After a warning, the woman shoots the neighbor down for trespassing on her property. After two hours, the injured man has bled to death. The woman decides that, after all, she likes better the grass growing freely. She returns to the house and calls the morgue. The market value of her property and of neighboring properties diminishes slightly, but justice will be served: she is suing the lawn mower producer for damages.
In a civilized society, force may be used only in retaliation and only against those who initiate its use. (Ayn Rand, The Virtue of Selfishness)
“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 non-aggressor. Here is the fundamental rule from which can be deduced the entire corpus of libertarian theory.” (Murray Rothbard, The Myth of National Defense)
Rules should be judged by the incentives they create, but there are no objective criteria for judging. Social experiments matter, while rational deduction can never really be distinguished from rationalization.