There are many test cases in which pure non-aggression, with full respect for property rights, leads to unacceptable results. David Friedman proposed one in which a killer is popping into a crowd, killing one innocent person after another. The only available gun with which to oppose him is lying in plain sight -- but its owner has threatened to prosecute anyone who touches it for any reason.
Solution: You seize the gun, drop the killer, and take your chances with the jury. Reasonable people will not put you away for committing a minor crime in defense of your life and the lives of innocent others.
Ralph Waldo Emerson said it best in his fabulous essay "Compensation," the contents of which are sufficient to govern any nation:
If the government is cruel, the governor's life is not safe. If you tax too high, the revenue will yield nothing. If you make the criminal code sanguinary, juries will fail to convict. If the law is too mild, private vengeance comes in.
Other interesting cases where pure non-aggression and ethical individualism -- the two tenets of libertarianism -- are insufficient also exist. I covered several in my essays on "The Conservative-Libertarian Schism," which are still available here at FreeRepublic. However, for ordinary interactions with sane and responsible individuals, they are more than sufficient: they are optimal.
Freedom, Wealth, and Peace,
Francis W. Porretto
Visit The Palace Of Reason: http://palaceofreason.com
Hardly.