Sources of law

The origins of law are the binding rules that allow a state to govern. The term "source of law" dates back to Cicero in Rome, who used it as a metaphor for a fountain—"fons" in Latin. In a technical sense, anything that can establish, alter, or abolish a right or law qualifies as a source. The phrase can also refer to the sovereign or the authority from which law gains its validity.

Legal theory typically divides sources into formal and material categories, though this division is not always applied consistently. Formal sources are generally linked to what creates law, such as statutes, case law, and contracts. Material sources, by contrast, are where formal law can be found—for example, official gazettes, newspapers, and public deeds. Drawing on Aristotle’s four causes (material, formal, efficient, and final), Riofrio identifies additional potential sources. Efficient sources include actions of nature or "of God" that alter law, intellectual actions that shape legal culture, and acts of will that approve laws and agreements. Final sources encompass the purposes of law, the intentions of parties in legal transactions, the goals of policies, and the ends of a constitution.

Jurisprudence influences the perceived authenticity of a source. A tyrant like Kim Jong-un may hold de facto power, but critics argue he lacks a de jure, or legitimate, source. After World War II, the Nuremberg trials rejected the defense of "only obeying orders," and Nazis were hanged for violating "universal and eternal standards of right and wrong." Over time, principles of law have emerged from customs. Early unwritten sources include the divine right of kings, natural and legal rights, human rights, civil rights, and common law. Historical or judicial precedent and case law can modify or create a source. Legislation, rules, and regulations form the tangible, codified, and enforceable sources of law.

In civil law systems, sources include legal codes—such as civil or criminal codes—and custom. Common law systems combine several sources to form "the law." These systems often borrow from each other; Scotland and South Africa, for instance, have hybrid legal systems—South Africa blending common law, civil law, and tribal law. A state may follow international law, have a written or federal constitution, or include regional legislatures, but the central national legislature is typically the ultimate source. A written constitution may appear primary, but the legislature can amend it under certain rules. International law can override national law, but it mainly consists of ratified conventions and treaties, which a national parliament may later denounce. Local authorities may pass by-laws based on a democratic mandate, but their legislative power is delegated by parliament, which can withdraw it.

In England, the archetypal common law country, sources are hierarchical: legislation (primary and secondary), case law rules of common law and equity, parliamentary conventions, general customs, books of authority, and canon law. Religious law, derived from sacred texts or doctrines, is significant where a state religion exists.

International treaties become binding only upon ratification. Most conventions take effect when a specified number of signatories have ratified the final text. An international convention may be incorporated into a statute—for example, the Hague–Visby Rules in the Carriage of Goods by Sea Act 1971, or the Salvage Convention in the Merchant Shipping Act 1995. The European Convention on Human Rights, from the Council of Europe, is enforced by the European Court of Human Rights in Strasbourg.

The European Union is a special case of international law. Member nations adopt all existing EC law—the acquis communautaire—including treaty provisions, regulations, directives, decisions, and precedents. They become subject to "Brussels" and the binding precedent of the Court of Justice of the European Union (CJEU) in Luxembourg. However, Brussels can only act within the EU treaties, and CJEU supremacy applies only to EU law matters.

Legislation is the primary source of law, consisting of legal rules declared by a competent authority. It serves many purposes: to regulate, authorize, enable, prohibit, fund, sanction, grant, declare, or restrict. A parliamentary legislature creates new laws—such as acts of Parliament—and amends or repeals old ones. It may delegate law-making powers to lower bodies. In the UK, delegated legislation includes statutory instruments, Orders in Council, and by-laws. Such legislation can be challenged for procedural irregularity, and the legislature can withdraw delegated powers. Most legislatures are constrained by a national constitution, and Montesquieu...