>There's never a lack of rules because we all understand natural law.
No we don't.
More to the point, I can guarantee that not everyone agrees with your understanding of whatever 'natural law' is, or with your inalienable right to exercise that view in their presence. Not even Libertarians agree on that.
It's not something for which there is "my understanding" and "your understanding".
It's obvious stuff. If you punch someone in the face you can expect retaliation. If you trade with others you can expect peace for the duration of that contract. And so on.
I'm not saying there's a list of the natural laws that I imagine people know of. There's no list. There's only the obvious stuff. Obviously I'd have to retaliate if I thought my life were in danger, and obviously I'd do my best to keep alliances that benefit me. Others will do the same. It all ends up working itself out. No need for a Hammurabi.
Even the most barbarian, uncivilized tribes have had a shaman or chieftain and a set of principles to follow and taboos to avoid. Arguably (since I Am Not An Archaologist), Hammurabi's insight wasn't having laws, but writing them down, and abstracting the force of law away from the immediate will of the god-king.
No we don't.
More to the point, I can guarantee that not everyone agrees with your understanding of whatever 'natural law' is, or with your inalienable right to exercise that view in their presence. Not even Libertarians agree on that.