Customary law

Customary law refers to a set of practices, customs, and beliefs that a community accepts as binding rules. Unlike many modern legal systems, these rules are not always written in formal codes. Instead, they emerge from established patterns of behavior within a specific social setting. For a practice to become customary law, it must meet a specific requirement called "opinio juris." This means the people acting must believe the practice is a legal necessity or a required opinion of law. These norms help regulate social behavior and provide a way to resolve disputes within a community.

In certain societies, such as the Tswana people, the system of norms functions with great flexibility. Scholars John Comaroff and Simon Roberts studied this in their work, "Rules and Processes." They identified two types of rules: "melao," which are rules pronounced by a chief, and "mekgwa," which are norms that become law through traditional usage. The Tswana often use an "undifferentiated normative repertoire." This means they do not always sort their many norms into strict categories. This lack of rigid classification allows for flexibility when settling disputes. It can even serve as a strategic resource for people trying to win a case.

This flexibility allows for the existence of incompatible norms. When two rules seem to conflict, the community may resolve the tension through context. Sometimes, a norm is moved from a "literal" meaning to a "symbolic" one. This allows both norms to exist in different realms of reality. Because of this, most norms are not viewed in isolation. Instead, they are negotiated based on the specific situation at hand. This process means the normative repertoire is always in a state of formation and transformation. New decisions in specific cases can actually change the rules over time.

Leadership plays a vital role in how these laws are created and enforced. In some cultures, a chief follows a specific process to propose a new norm. The chief first discusses the idea with advisors, then with a council of headmen. After that, a public assembly debates the proposed law. The assembly may choose to accept or reject the proposal. While a chief can proclaim a law even if the assembly rejects it, doing so is rare. The effectiveness of a law depends on the chief's legitimacy. It also depends on whether the law matches the will and practices of the people.

Some scholars have debated how to define these social rules. John Hund studied the ideas of H. L. A. Hart to address "rule scepticism." This is the doubt that customary practices are actually objective rules. Hund used Hart's work to distinguish between a simple habit and a social rule. A habit is just an external, observable behavior that people do often. A social rule has an "internal aspect," meaning people feel an obligation to follow it. Members of a group follow social rules because they see them as a common standard. They may even criticize others who deviate from these standards.

Historically, these unwritten traditions were sometimes collected into written books. These collections were known as "custumals." They were used in medieval Europe to manage local jurisdictions, such as a specific manor or borough. Over time, jurists pieced these together from local case law. Famous examples include Bracton's for England and various collections for Paris, northern Germany, and Spain. These documents helped regulate the rights, entitlements, and obligations of community members. They turned local traditions into a recognized force of law.

Today, customary law also plays a major role in international relations. This is often called the "Law of Nations." It involves legal norms that develop through the consistent exchanges between different states. These obligations arise because states act in ways that follow past accepted conduct. Some of these international customs are so strong they are called "peremptory norms." These are rules that cannot be violated or changed, such as the prohibitions against slavery and genocide. These norms gain their power from being accepted almost universally by the world's nations.