Full Idea
A state may not use its coercive apparatus for the purposes of getting some citizens to aid others, or in order to prohibit activities to people for their own good or protection.
Gist of Idea
States can't enforce mutual aid on citizens, or interfere for their own good
Source
Robert Nozick (Anarchy,State, and Utopia [1974], Pref)
Book Reference
Nozick,Robert: 'Anarchy,State, and Utopia' [Blackwell 1980], p.-8
A Reaction
You certainly can't apply these principles to children, so becoming an 'adult' seems to be a very profound step in Nozick's account. At what age must we stop interfering with people for their own good. If the state is prohibited, are neighbours also?