all societies have rules otherwise they would descend into anarchy. And the basis of all consensual laws (as opposed to imposed) is the customary or informal rule-sets that have been evolving with the society. These rule-sets must be rationalized and formalized (and yes, modernized) as a part of creating a true nation, but laws cannot be imposed if one expects them to be observed.
...Once the national law establishes common rules for peoples' property and savings - mainly their homes and businesses - Iraqi citizens can then get about working, saving and doing business with (not killing) one another. There will always be fanatics, but most people with jobs and a shot at a future don't blow themselves up.
It is easy to agree with Schaefer that our approach in Iraq to this point is not working. It is easy to agree that a system of law that emerges from common law is more likely to take hold than a top-down Constitution. However, I am doubtful that the United States can, from the outside, create a common-law environment in Iraq.