Civil law is primarily contrasted against common law, which is the legal system developed among Anglo-Saxon people, especially in Britain.
The original difference is that, historically, common law was law developed by custom, beginning before there were any written laws and continuing to be applied by courts after there were written laws, too, whereas civil law developed out of the Roman law of Justinian's Corpus Juris Civilis (Body of Civil Law).
In later times, civil law became codified as droit coutumier or customary law that were local compilations of legal principles recognized as normative. Sparked by the age of enlightenment, attempts to codify private law began during the second half of the 18th century (see civil code), but civil codes with a lasting influence were promulgated only after the French Revolution, in jurisdictions such as France (with its Napoleonic Code), Austria (see ABGB), Quebec (see Civil Code of Quebec), Italy (Codice Civile), Spain (Código Civil), the Netherlands and Germany (see Bürgerliches Gesetzbuch). However, codification is by no means a defining characteristic of a civil law system, as e.g. the civil law systems of Scandinavian countries remain largely uncodified , whereas common law jurisdictions have frequently codified parts of their laws, e.g. in the U.S. Uniform Commercial Code. There are also mixed systems, such as the laws of Scotland, Louisiana, Quebec, the Philippines, Namibia and South Africa.
Thus, the difference between civil law and common law lies not just in the mere fact of codification, but in the methodological approach to codes and statutes. In civil law countries, legislation is seen as the primary source of law. By default, courts thus base their judgments on the provisions of codes and statutes, from which solutions in particular cases are to be derived. Courts thus have to reason extensively on the basis of general rules and principles of the code, often drawing analogies from statutory provisions to fill lacunae and to achieve coherence. By contrast, in the common law system, cases are the primary source of law, while statutes are only seen as incursions into the common law and thus interpreted narrowly.
The underlying principle of separation of powers is seen somewhat differently in civil law and common law countries. In some common law countries, especially the United States, judges are seen as balancing the power of the other branches of government. By contrast, the original idea of separation of powers in France was to assign different roles to legislation and to judges, with the latter only applying the law (the judge as la bouche de la loi; 'the mouth of the law'). This translates into the fact that many civil law jurisdictions reject the formalistic notion of binding precedent (although paying due consideration to settled case-law), or restrict the power to set precedents to a competent Supreme Court.
There are other notable differences between the legal methodologies of various civil law countries. For example, it is often said that common law opinions are much longer and contain elaborate reasoning, whereas legal opinions in civil law countries are usually very short and formal in nature. This is in principle true in France, where judges cite only legislation, but not prior case law. (However, this does not mean that judges do not consider it when drafting opinions.) By contrast, court opinions in German-speaking countries can be as long as English ones, and normally discuss prior cases and academic writing extensively.
There are, however, certain sociological differences. In some Civil law countries judges are trained and promoted separately from attorneys, whereas common law judges are usually selected from accomplished and reputable attorneys. In the Scandinavian countries judges are attorneys who have applied for the position, whereas France has a specialized graduate school for judges.
With respect to criminal procedure, certain civil law systems are based upon a variant of the inquisitorial system rather than the adversarial system. In common law countries, this kind of judicial organization is sometimes criticized as lacking a presumption of innocence. Most European countries, however, are parties to the European Convention on Human Rights and Article 6 guarantees "the right to a fair trial" and the presumption of innocence. The Convention is ratified by all the members and as such part of their national legislation. Some Civil law nations also have legislation that predates the Convention and secures the defendant the presumption of innocence. Amongst them Norway where the presumption is guaranteed by uncodified customary law and validated theory recognized by the Supreme Court in plenary (effectively forming a precedent).
While the presumption of innocence is present, what distinguishes the more inquisitorial system is the frequent lack of a jury of peers, which is guaranteed in many common law jurisdictions. Inquisitorial systems tend to have something akin to a "bench" trial made up of a single judge or a tribunal. Some Scandinavian nations have a tribunal that consists of one civilian and two trained legal professionals. One result of the inquisitorial system's lack of jury trial is a significant difference in the rules of trial evidence. Common law rules of evidence are founded a concern that juries will misuse, or give inappropriate weight to unreliable evidence. In inquisitorial systems the rules of evidence are sometimes less complicated because legal professionals are considered capable of identifying reliable evidence. Most noteworthy of these is the lack of a hearsay rule. The common law hearsay rule has roughly 32 exceptions to its ban on the use of out-of-court statements.
The term "civil law" as applied to a legal tradition actually originates in English-speaking countries, where it was used to lump all non-English legal traditions together and contrast them to the English common law. However, since continental European traditions are by no means uniform, scholars of comparative law and economists promoting the legal origins theory usually subdivide civil law into four distinct groups:
French civil law: in France, the Benelux countries, The Canadian Province of Quebec, Italy, Spain and former colonies of those countries;
German civil law: in Germany, Austria, Switzerland, Greece, Portugal, Turkey, Japan, South Korea and the Republic of China;
Scandinavian civil law: in Denmark, Finland, Iceland, Norway and Sweden.
Chinese law is a mixture of civil law and socialist law.
Portugal, Brazil and Italy have evolved from French to German influence, as their 19th century civil codes were close to the Napoleonic Code and their 20th century civil codes are much closer to the German Bürgerliches Gesetzbuch. Legal culture and law schools have also come near to the German system. The other law in these countries is often said to be of a hybrid nature.
The Dutch law, or at least the Dutch civil code (called the Burgerlijk Wetboek) cannot be easily placed in one of the mentioned groups either, and it has itself influenced the modern private law of other countries. The present Russian civil code is in part a translation of the Dutch one.