No doubt this will be downvoted, but I would go with some basic legal texts. The law has been part of civilization from the beginning (Hammurabi). Something like Blacks Law Dictionary would be vitally important in setting up a reliable system post-zombie.
I tend to agree that if there's a civilization, there are laws, but your example is bizarre. A quick check of wikipedia informs us that Hammurabi was born circa 1810 BC. Compare Sargon, who took his throne about 500 years prior, or Narmer, who unified Egypt over a thousand years before Hammurabi was born. And we only know about them because they left records. The Egyptians also left records of various near-eastern peoples who clearly had flourishing civilizations at the time, but left no records of themselves. These great conquerors come from a backdrop of states that are already old.
Seven thousand years ago, pre-Egyptian nomads left religious art in what is now the Sahara desert (though at the time they used it to pasture their animals). Nomads aren't traditionally considered civilized; we like to use agriculture as the threshold. But those nomads surely had laws, even if you'd find them primitive, and they were organized enough to leave monuments behind and, eventually, conquer the farmers who lived along the Nile and set themselves up as the ruling class.
There other, older, legal traditions but they rarely are relevant to modern jurisprudence.
And I responded to you saying that Hammurabi was the beginning of civilization, which is even more ludicrous.
That is basically how the common law functions today. Harm people and you are personally punished. Harm property and you must pay for that property. Criminal law and civil law, crimes and torts.
*Of course the "property" in the original were actually slaves, but the principal holds.
200. If a man knock out the teeth of his equal,
his teeth shall be knocked out.
201. If he knock out the teeth of a freed man,
he shall pay one-third of a gold mina.
202. If any one strike the body of a man higher in rank than he,
he shall receive sixty blows with an ox-whip in public.
203. If a free-born man strike the body of another free-born man or equal rank,
he shall pay one gold mina.
204. If a freed man strike the body of another freed man,
he shall pay ten shekels in money.
Here are a couple more interesting clauses:
108. If a tavern-keeper (feminine) does not accept corn according to gross weight
in payment of drink, but takes money, and the price of the drink is less
than that of the corn, she shall be convicted and thrown into the water.
114. If a man have no claim on another for corn and money, and try to
demand it by force, he shall pay one-third of a mina of silver in every case.
And, again, there is no cultural continuity from mesopotamia to modern europe or america. Similarity between Hammurabi's Code and the English common law does not represent influence of one on the other, it represents parallel evolution. It is therefore no more and no less relevant to understanding the common law than, say, early Indian law, or 1700s Japanese law.
Other civilizations have got by just fine without them, and maybe without tainting influences, the survivors will do better next time.
E.g. too many of these things require fixed assets and a framework where nomadic raiders are kept from totally despoiling those and the people working on them, the classic example being agriculture and farmers. Sans that, you might have something called "civilization", but it won't support very many people, and it won't be pretty. Or you might collapse all the way down to small, hostile to each other bands of hunter-gatherers. I seem to remember reading in Guns, Germs and Steel that the Australian aborigines came from a civilization that farmed....
The paints 'civilized law' as authoritarian, vengance based, and using primitive means to try to alter behavior.