The "No True Libertarianism" fallacy/gangs
From Critiques Of Libertarianism
Urban street gangs in under-policed neighborhoods, mafias in under-taxed countries, and groups like Hezbollah in Lebanon invariably step in to fill the void where government fails. When the Japanese government wasn't able to adequately help the population after the earthquake and tsunami, the yakuza helpfully stepped in to do it for them. The devolution of local authority and taxation into the hands of criminal groups willing to provide a safety net in exchange for their cut of the action is the invariable pre-feudal result of the breakdown of the government-backed safety net. It happens every single time. The people will want a safety net where utter chaos doesn't prevent it: they'll either get it from an accountable governmental authority, or from a non-governmental authority of shadowy legality. Both kinds of authority will levy their own form of taxation, be it legal and official, or part of an illegal protection scheme.
David Atkins, "The "No True Libertarianism" fallacy"