A legal tradition is a set of deeply rooted and historically conditioned attitudes about the law. The civil law tradition is the oldest and most widespread legal tradition of the world.

The oldest layer of the civil law tradition is the Roman law developed beginning in the fifth century BC, which flourished between the first and third centuries BC. Two other layers are canon law, developed by the Catholic Church for the governance of the faithful and of the church itself, and the commercial law developed by the Italian merchant guilds in late medieval times.

The French Revolution provided many of the ideas of the present-day civil law tradition: the rationalization of law, its association with the state, the equality of citizens, and the importance of rights were key aspects of the French Revolution, and they are still at the center of the civil law tradition conception of law.

The strengthening of nation-states in Europe and the generalization of the separation of government branches promoted the idea that the law was associated with statutes and that these were the main source of law.

The codification of law has been perceived as a typical character of the legal systems of the civil law tradition. Nevertheless, codes exist in common law jurisdictions, and some civil law countries have not codified their law. The difference is that codes play a central role in civil law countries, while they have a modest place in a country like the United States.

Contrary to the common law tradition, in which judges have a central role, judges in the civil law tradition are conceived of as civil servants whose role is to apply the legislation in a mechanical way. This conception has been contested by scholarship, and the increased importance of constitutions and constitutional review has strengthened judges' role.

Codes and legislation are supposed to be clear and unambiguous so as to provide an easy resolution of cases before judges. In practice, things are more complex, and judges and other readers need to "interpret" the legislation. Initially, judges were denied this power, and interpretation rested with the legislature itself and special bodies in the legislative branch, such as the Cour de Cassation in France. In general, scholars today recognize that judges interpret the law and that there is little difference in this regard between the civil law and the common law traditions.

In the civil law tradition, legal certainty is a supreme value, which gives a certain rigidity to the legal systems within this tradition. The concept of equity is a way of giving flexibility to judges, but equity has a very limited place in the civil law tradition. This is another reason for the reduced role of judges in this tradition.

Unlike the common law, in which judges have a central role, the central figure in the civil law tradition is the professor-scholar. These scholars are responsible for elaboration of codes and legislation and are considered the most authoritative figures for interpretation of these legal documents. In this respect, the civil and common law traditions are increasingly similar. In the common law countries, scholars have played a more prominent role as law schools in United States and other common law countries have been strengthened.

In nineteenth-century Germany, scholars developed "legal science": an elaboration of concepts and principles starting from positive legal rules. This innovation was quickly accepted in other civil law countries, even if there has been persistent resistance for those who look to interests and the social and economic context of law.

There is a set of general concepts built by legal scholars that can appear in the preliminary part of the civil code and are considered general principles of law. The central idea is that the law is composed of norms, and norms established by the state are the only true law (or "positive law"), but there are principles that are supposed to apply to the construction and interpretation of norms that are beyond the reach of legislators.

A common perception of the legal process in the civil law countries is that legal scholars take care of the systematic statement of law and that legislators, inspired by them, improve the legislation to make it gapless and logical consistent. Judges' role is the mechanical application of law. In practice, things are more complex. Legal scholars have different viewpoints, and legislation tries to respond to policy issues. Judges are more important than accepted by the model. Many scholars are critical of this way of thinking the legal process and have introduced economic, social, and policy considerations in the analysis of law, but the traditional "dogmatic" way of thinking of the law persists in most law schools.

While in the common law countries the courts tend to have jurisdiction over all law fields, in the civil law countries there is a set of administrative and constitutional courts separated from the courts of general jurisdiction. The reason is a very rigid idea of separation of the different branches of public power.

The distinction between private law and public law is considered fundamental in the civil law tradition. Private law regulates the relation among citizens: the state establishes the general rules and is the arbiter or adjudicator in their conflicts. In the public law, the state is a party. Principles, rules, and jurisdictions are supposed to be different. In practice, things are more complex, and the distinction—or more generally the distinction between branches of law—is less important in present-day legal scholarship.

Civil law professionals have specialized careers. After law school, they have to choose which additional training they will receive to become judges, prosecutors, advocates, notaries, and so on. Within each career path there is frequently vertical advancement, but horizontal mobility is infrequent.

The typical civil proceeding in a civil law country is actually a series of isolated meetings and written communications between counsel and the judge, in which evidence is introduced, testimony is given, and procedural motions and rulings are made. There is no trial in the sense known in the common law. Appeals are frequent, and appellate judges have the power to reanalyze evidence.

The traditional type of criminal procedure in the civil law countries is "inquisitorial" in the sense that the judge had to look for the truth, or the elements required for conviction. The common law criminal procedure is considered "accusatorial" in the sense that accuser or prosecutor has a central role, as well as defender. The judge moderates the debate, hears the parties, and instructs the jury. More recent changes in criminal law procedure incorporate many elements of the accusatorial style, including the plea bargain, a negotiation between prosecutor and defender to accelerate the procedure in exchange for leniency.

The civil law countries are moving away from the idea of legislative supremacy and the subdued role of judges. First, the need to control the public administration led to the role of an administrative justice. Later, the conviction that the constitution should not be modified by legislation led to constitutional review. Some civil law countries, following the example of the United States, rest the power of constitutional review in the Supreme Court, while other countries have preferred to create a special constitutional court.

The civil law tradition offers important variations from country to country, much of which are related to different national political, cultural, and economic histories. The civil law tradition is also constantly changing not only because of the pressure of external forces but also because of the constant criticism of its own scholars.

Traditions change, including those of the civil law. In our time the loss of the importance of codes (decodification) and the increase in special legislation and judge-made law are visible. Also evident is the increased importance of the constitution and constitutional courts and judges. Finally, there is a tendency toward strengthening international courts and fora. In Europe this tendency has taken the form of a federalization.