Many anarcho-capitalists deny there is a need to “handle” such problems at all. The implicit assumption in the question is that a) freeloading, or b) services which cannot get funding voluntarily due to individual rationality issues, somehow justify the use of aggression. Those who support the NAP deny this assumption.
Another approach is to point out that, in these cases, the State does not really solve the public goods problem. It merely creates a bigger, more intractable public goods problem — how to limit State power. As Friedman points out, in a statist society good law is a public good and bad “special interest” law is a private good. So the result is that good law is undersupplied and bad law is oversupplied. By shifting the problem to State authority, you simply contribute to the hell that Bastiat warned us about, where “everybody plunders everybody.”
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