The idea of anarchy means, "no ruler", remember? A ruler might be anyone or anything, which enforces a given set of rules (laws). This means, that when anarchy suggests, getting rid of rulers, it suggests getting rid of universal laws. - a single set of rules being enforced on everyone in a given territory and opening up the debate to multiple, competing, voluntary sets of rules.
Ok, there's no ruler, no universal laws anymore, and so why do you think there will be a new shiny set of rules everyone on the block agrees upon? People are different and even between two people you will get a disagreeing minority...
There is no universal law now. Where is the world ruler and his/their laws that we all have to follow?
We currently have competing law providers that we are "contracted" to. I use contract loosely of course, because there is no such thing.
Why should a law provider be bound to a certain patch of land and no other law providers be able to operate in the same territory? If we had competition we could make actually choices about what we deem to be good laws and if we don't think our provider is doing a good job, we can end the contract and pick another law provider, without having to go through the hassle of emigration.