Anarchists in general are quite negative to the prison system and often believes in alternatives, or at the very least tries to come up with alternatives (hard as that might be).

That being said, there are certainly situations where people with anarchism (or anarchism-like) beliefs have essentially jailed people. For example YPG/YPJ forces in Rojava certainly took IS/ISIL forces they won over as prisoners.

PS: Never ever heard of an anarchist that thinks the US prison system is anywhere near of justifying itself though, but that's probably something all radical leftists agree on.