Canada

You're getting downvoted by the ACAB brigade. But you're absolutely right. If there is zero enforcement of the Rule of Law, then the Rule of Law doesn't exist. Granted cops are only a portion of that mechanism (legal system and legislators and general societal acceptance of these institutions also required.)

You could run an experiment -- remove all cops from Calgary, but keep cops in Edmonton. The crime rate might be similar to background in the first year, but in the third year? Tenth year? I'd suspect that suddenly people would be clamouring for the police to enforce laws in Calgary again.

(I picked those cities because there was a remarkable experiment performed at one point where Calgary stopped fluorinating their water supply, while Edmonton continued. The cavity rates diverged rapidly until political pressure returned fluorination.)

Anyway, a background level of policing is required for Peace, Order, and Good Governance. Not zero police. Not a police state either.