Reputation and peer pressure are pretty effective at compelling people to act justly (according to the local consensus definition) even in the absence of a form

Reputation and peer pressure are pretty effective at compelling people to act justly (according to the local consensus definition) even in the absence of a formal legal system. If reputation and peer pressure scaled to group sizes bigger than Dunbar's number (i.e. about a hundred or so) then we probably wouldn't need laws at all. I suppose you one might say that social expectations are just another kind of law, in which case, yeah it's hard to imagine any group of people without some kind of expectations of how each other will behave. That's kind of the basis of human relationships.