It doesn't have to be a legal system or a government in general. E.g. Rai stones are basically a public ledger system akin to a blockchain, but working through social convention.

https://en.wikipedia.org/wiki/Rai_stones

One could argue that, in this case, the entire society is "people with guns". Which is fair enough, but, again, it's important to keep in mind that this concept does not intrinsically require anything equivalent to the modern state.