Anarchy is ’no rulers’ not ’no rules’. If someone is going to do something harmful for the community, you don’t just let them. You are actively incentivised to stop them, because it’s your obligation as a member of the community.
Which reduces matters to force vs. force; and for that matter, is much more directly an individual making decisions for other individuals than most modern states.
No rulers cannot also mean no enforcement beyond individual action, because that effectively means no rules.