Law is an expression of rights and duties, and is a set of rules. In codified jurisdictions, laws are accessible to citizens and enforced by a controlling authority. Violation of these rules can result in criminal and civil penalties. In the United States, laws are enacted by the federal, state and local legislatures, as well as by judges and administrative agencies. Although primarily a legislative system, laws can also serve a practical purpose, such as creating rules that protect property rights.

One important function of law is the monopolization of violence in society. This function is the most important, according to Hans Kelsen. However, H.L.A. Hart argued that it is less important than the normative aspect of law. Law is the only means of preventing or punishing violations of human rights, so it should be seen as a useful tool in protecting society. Although law is a valuable tool, it is not without faults.

In some countries, there are different systems of law. Some countries use a combination of common and civil law. In South Africa, the Roman-Dutch legal system is based on the older, uncodified civil law of Holland. The system also governs the law in Namibia, Lesotho and Zambia. The Dutch legal system is distinguished by its extensive body of juristic literature that dates back to Hugo Grotius de Groot in the seventeenth century.