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there is no set way to proceed.
https://theanarchistlibrary.org/library/peter-gelderloos-anarchy-works
That book goes over cases in history where systems like this were in place.

What I would do is tie the person up, call a town meeting, and decide what to do from there. Maybe I won't have enough time, and my only solution will be to shoot them. It all comes down to the individual decisions of those involved. Some might not call a local council, some may create a specific force dedicated to this. Who knows

mmmm I see ... but if there are no rules, why would a meeting be called or why would someone who would kill or abuse someone else be punished in any way? Is there a principle or something?

how about you read that book, it goes into detail on any situation you could throw at me here with actual historical examples

a meeting would be called because we want to call a meeting. It's that simple. It turns out people are perfectly capable of doing things when there isn't a gun pointed at their head