NAP, aka respect for private property rights. If a society does not respect the NAP then it is a society based foremost on the threat of violence. What is government - the threat of violence - the threat of force. So, if a society allowed private militia to kill competitors you would end up with a gang ruling over others - you know - like government. So, yes you need a society with respect for private property rights/NAP. Would all people be peaceful? Heck no! Does this mean there will also not be private institutions that uphold the law - uphold respect for private property rights? Of course! People will still need security, decision making and justice! A peaceful society with respect for the NAP would NOT allow a private militia to violate others rights! Business (in the absence of government favouritism) survives on good products, services and reputation. Sending a militia against you opponents does not do well for your reputation! So ultimately you have a choice - government, which is an involuntary institution with a monopoly on force and rule making that serves the elite to the detriment of others OR A free society with respect for private property rights that is more decentralised and snuffs out any trouble makers.