America has been blessed with the English common law system, or customary law based largely on precedent and statutes in effect in England under James I in 1603. Many of the former English Colonies adopted the common law system. Continental Europe, on the other-hand, and many other countries adopted a civil law system based on detailed written codes.
The civil law system traces its origins to the ancient Roman law system. The most famous of these civil law systems is the "Code Napoleon" of 1804, which serves as the basis for modern French law.
It is widely recognized that the "rule of law" is necessary for a civil and prosperous society. But in order to have a "rule of law," people need to know what the law is and for the laws to be considered reasonable. The Ten Commandments are an example of this principle. Most everyone could memorize 10 rules, but no person can know 10,000 or 100,000 rules. The beauty of the traditional common law system was there were relatively few rules, and the subsequent development of the law was based on the commonly understood first principles. Thou shall not murder, steal, etc.
Unfortunately, in recent decades we have had an explosion in detailed rulemaking that has drifted far from the common law. For instance, 30 percent of all federal criminal laws have been passed since 1970. Before 1950, most Americans could pretty well know whether an action they might undertake would violate the law. That has now changed.
In my specialty, antitrust, the problem of civil law is on full display. I'm always amazed that there are literally hundreds of otherwise law-abiding businesses that somehow manage to violate the antitrust "laws" despite retaining highly competent (and highly paid) legal counsel to advise them on antitrust matters. If antitrust law was objective and concise—that is to say, if it was understandable by the commoner—you wouldn't see the plethora of merger reveiews and FTC consent orders you see today. Indeed, the FTC would probably be out of the antitrust business altogether, since no rational business would deliberately incur the agency's wrath.