The whole argument rests on the idea that obligations can't be inherited, that no man has any duty to which he has not consciously and explicitly agreed.
The libertarian lauds custom and unarticulated knowledge when the state seeks to impose a new constraint upon him.
The libertarian praises explicit articulated consent when he rebels against a constraint to which his neighbors are accustomed.
This is why Karen D'costa gets nervous if someone theorizes about a gated community in which the housing authority is granted any power of eminent domain, while not denying its consistency with libertarian Principle.