Everyone sort of enforces the rules as they see fit now. The difference is there is an expectation to not resist when someone is abusing their power because they are an authority figure. Under anarchism, it is your peers holding each other accountable, and your right to question actions against you is accepted.

I look at it the other way. In a free and prosperous armed society where common sense rules are respected and insisted upon by the majority who would be stupid enough to break the rules? Let us look at it some other ways. Ebay is one of the largest merchant structures in the world. It is not an authority, but has for decades now used in-house arbitration for disputes. Detroit has a private 'police force'. It is not an authority. It is a private defence org that also runs a volunteer community protection unit that uses psychology as its main policing tool. Historically we had Panarchy in Ireland. People regardless of territory could voluntarily join a tuath. It would offer legal services. If unsatisfactory the client could join another tuath. Even today way much more is spent on private security than on policing. Maratine law orignally ran on banishment. Did not pay your contract or larder bill. You could no longer dock your ship or be served at a tavern etc. Before the state co-opted the law, there was Common Law! Law does not require authority.