Near where I live a migrant worker recently murdered another over a $1 or $2 gambling game. According to the rather gore-loving local police he nearly decapitated him (that's where I got my NITT idea from)
How would you prevent people like that from cutting each others heads off in your world without rules?
How many things are wrong with this question?
Anarchism means without rulers, not without rules.
The world we have today, with rulers, failed to stop the migrant worker from murdering another migrant worker.
If a world without rulers also failed to stop the migrant worker, this would not represent a failure of anarchism any more than the murder that
did happen represents the failure of government.
So your question itself is wrong.
We live in a world that, despite numerous laws and extraordinarily expensive law enforcement agencies, still fails to stop migrant workers for murdering each other over a $1 or $2 gambling game.
Why not live in a world where those murders also happen, but at least we don't have to pay the salaries of a bunch of people who fail to keep their promises to prevent it?