To expound on the comparison between “common law” and “civil law” traditions, and offer a U.S. lawyer's point of view:
The term “common law” distinguishes the Anglo-American legal system from the “civil” or “civilian” legal systems of Continental Europe. “Civil” law is based exclusively on a written code. The “common law” basically divides the law into two categories: (1) a code, or statutes enacted by the sovereign, and (2) case law which presupposes a body of custom and policy norms independent of positive, statutory law.
These distinctions do not apply to modern criminal law. They apply to the legal relations between private individuals: property, contract and tort law. Stereotypically, “civil” law looks to evolving international consensus, the “enlightened” view of civilized peoples, whereas “common law” looks backward at cherished local traditions and privileges. Either approach, of course, lends itself to fabrication. One can just as well look forward to a perfect world that never will be, as back to past eras of harmony and freedom that never were.
As Gritchka relates, “common law” derives from a long history of wars, rebellions and revolutions, a never quite conquered Saxon people and a landed gentry which was never tamed by Church or Crown. “Civil” law, on the other hand, is a more modern invention. It reflects the absolute and despotic control of the modern nation-state over the people. While it is true (as Gritchka’s writeup says) that the “civil” tradition ultimately derives from Roman law, especially the Corpus Juris Civilis of Emperor Justinian, the Roman Empire did not impose the civilian tradition in, for example, Germany. Rather, most of the countries which now have a "civilian" tradition were ruled by Napoleon, and subject to the Napoleonic Code. While France’s empire did not last long, the influence of the Napoleonic Code did. It has evolved into a “private international law” in continental Europe.
Other countries, such as Japan, deliberately adopted a “civil” tradition in an effort to modernize (read: Europeanize) their legal systems to engage in international trade. Why Scotland employs a mix of “common law” and “civil law” is something only law professors at Edinburgh probably understand.
In the Americas, Quebec and Louisiana have “civil law” traditions, because these provinces were former French colonies. The influence of “civil” law in former Spanish territories, such as California, Arizona, New Mexico and Texas, is much more subtle. An example would be the tradition of “community property” of married persons.
As a practical matter, while human ingenuity knows no limits, and lawyers and judges can certainly come up with many and varied ways of interpreting a code, “civil” law is relatively impervious to obfuscation. “Common law”, on the other hand, encourages it. “Common law” bases its understanding of unwritten custom or policy norms on a mass of confusing and contradictory precedents. It revels in the tensions between rules and exceptions, national and local interests, and old and new. As a practical matter, getting away with things is considerably easier under the “common law”. Statutes seem to be written to be evaded, not enforced. This hostility to written rules comes from a long tradition of defending individual liberties and freedoms against the despotic rule of the Crown, or a mob in Parliament.
In the United States, the “common law” tradition of defending fundamental rights and liberties has been subsumed into “constitutional” law. While theoretically the Constitution is a legal “code”, it was not written like a civil code and it is not interpreted like one. U.S. jurists use the Constitution to reign in the sovereign. This has nothing to do with politics: liberal or conservative. Whether striking down apartheid, like the Warren Court did, or striking down civil rights laws, like the current Court does, the United States Supreme Court interprets the Constitution broadly against a background of policy norms. The Constitution’s grandfather is Magna Carta, not the Code Napoleon.