Common Law

Common law is a legal system built primarily from the accumulated decisions judges make in deciding individual court cases, rather than from a comprehensive legal code written in advance by a legislature. It forms the foundation of the legal systems in the United States, England and Wales, India, Canada outside Quebec, and many other countries with historical ties to England, standing in contrast to civil law systems, whose rules derive mainly from codified statutes.

Medieval English origins

Before the twelfth century, England had no single justice system applied consistently across the whole country, relying instead on a patchwork of local customs and competing courts. King Henry II changed this by sending royal judges on regular circuits throughout the kingdom to hear cases, applying a body of law developed by judges based at Westminster. Because this law was meant to apply equally everywhere rather than varying by locality, it became known as the common law, common in the sense of being shared across the whole realm. The 1215 Magna Carta later reinforced the system by protecting the right to trial by jury, and over subsequent centuries, common law gradually came to dominate rival English legal traditions, including ecclesiastical courts, local customary law, and the Roman-influenced law once used in certain specialized courts.

Precedent and stare decisis

The defining mechanism of common law is judicial precedent, governed by the doctrine of stare decisis, Latin for “to stand by things decided.” Under this principle, a court’s ruling on a particular legal question generally binds that court and lower courts within the same jurisdiction when they face materially similar facts in future cases. This creates a strong degree of predictability and consistency, since parties and their lawyers can look to past decisions to anticipate how a new dispute is likely to be resolved.

Precedent does not freeze the law in place, however. Judges retain meaningful power to distinguish a new case from an earlier precedent by identifying factual differences significant enough to justify a different outcome, which gives common law systems a built-in capacity to adapt gradually to new circumstances without requiring legislative intervention every time. This case-by-case evolution is often cited as both common law’s greatest strength, its flexibility and responsiveness to real-world facts, and a recurring source of criticism, since the law on a given question can sometimes remain genuinely unsettled until enough cases accumulate to clarify it.

The adversarial process

Common law systems typically resolve disputes through an adversarial process, in which two opposing parties each present their own evidence and legal arguments, while a judge serves as a neutral arbiter who applies the law and decides the outcome, rather than independently investigating the facts. This contrasts with the inquisitorial model found in many civil law countries, where judges take a more active role in gathering evidence and directing the investigation themselves. The adversarial structure places substantial responsibility on lawyers for each side to build and present the strongest possible case, with the judge, and in many cases a jury, ultimately weighing the competing arguments and evidence presented.

Spread beyond England

English common law spread extensively through Britain’s colonial expansion, and its influence today remains strongest in former British territories, including the United States, Canada, Australia, India, and numerous other Commonwealth nations. Even within countries generally built on common law, pockets of other legal traditions sometimes persist for historical reasons; several southwestern US states, for example, retain some civil law influence inherited from their earlier history under Spanish and Mexican rule, particularly in areas like property and water rights.

Common law also differs from civil law in its basic source of authority: common law derives from judicial decisions accumulated over time, while civil law systems, which developed in continental Europe and spread through Spanish, Portuguese, and other European colonial empires, rely primarily on comprehensive legal codes drafted and enacted by legislatures, with judicial decisions playing a comparatively secondary interpretive role rather than serving as binding precedent in the common law sense.

Common law and equity

For centuries, English common law operated alongside a parallel system called equity, administered through separate Courts of Chancery rather than the ordinary common law courts. Equity developed specifically to address situations where the rigid, formulaic remedies available under strict common law, chiefly monetary damages, could not adequately address an injustice, offering more flexible remedies such as injunctions and specific performance instead. Over time, most common law jurisdictions merged their common law and equity courts into a single unified court system, though the underlying distinction between legal and equitable remedies still shapes how modern courts decide which kind of relief is appropriate in a given case, even though a single court now typically has authority to grant either kind, a legacy that still influences legal education and terminology in common law countries today.

FAQs

• What does stare decisis mean? Stare decisis is the doctrine that courts should follow precedent, generally meaning a court’s past decisions bind that court and lower courts when deciding materially similar future cases.
• How does common law differ from civil law systems? Common law derives primarily from judicial decisions built up case by case, while civil law systems rely mainly on comprehensive codes enacted by legislatures.
• What is the difference between common law and equity? Common law traditionally offered mainly monetary damages through its own courts, while equity, once administered separately through Courts of Chancery, provided more flexible remedies like injunctions; most jurisdictions have since merged the two into one court system.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 2, 2026Researched and drafted with AI assistanceReport an issue