harm principle It is often suggested, sometimes even by *libertarians,
that actions that harm other people should not be allowed. But taken literally,
this cannot be correct. For we often *objectively harm others, or *risk
harming them, with their permission: such as by providing them with ‘junk
food’, cigarettes, or participatory *sports. Harming, or risking harming, others on a voluntary
basis is part of *liberty. A better criterion of what should not be allowed
is what *proactively imposes on other people (or normal adults,
at least; with the mentally impaired, etc., being treated like *children
of similar intellect), even if it does the imposed-on people some objective good.

A Dictionary of Libertarianism