Common law is a legal tradition that originated in medieval England and spread through British colonial influence to jurisdictions including the United States, Canada (except Quebec), Australia, New Zealand, India, and much of the Anglophone Caribbean and Africa. Its defining feature is stare decisis—the doctrine that courts are bound by the principles established in prior judicial decisions of higher courts within the same jurisdiction.
Unlike civil law systems, which derive primarily from comprehensive written codes (descended from Roman law and the Napoleonic Code of 1804), common law develops incrementally through case-by-case adjudication. Judges interpret statutes, but they also create binding legal rules where legislation is silent or ambiguous. Over time, accumulated rulings form a body of precedent that functions as law alongside statutes.
Key characteristics include:
- Adversarial procedure, in which opposing parties present evidence to a relatively passive judge or jury, rather than the inquisitorial model common in civil law systems.
- Judge-made law in areas such as torts, contracts, and property, much of which was never codified.
- Equity, a parallel body of remedies (injunctions, specific performance) historically developed by the English Court of Chancery and largely fused with common law courts in the late 19th century.
For international relations, the common law/civil law distinction matters in several ways. It shapes how states approach treaty interpretation, the domestic incorporation of international law (monist versus dualist approaches often correlate with legal tradition), and the drafting style of international instruments. The International Court of Justice's Statute, in Article 38, lists "judicial decisions" and "the teachings of the most highly qualified publicists" as subsidiary sources of international law—a compromise reflecting both traditions.
Common law jurisdictions have also been disproportionately influential in international commercial arbitration and in shaping bodies such as the WTO Appellate Body, where reasoning from precedent, though not formally binding, plays a significant role.
Example
In the 2022 case Dobbs v. Jackson Women's Health Organization, the U.S. Supreme Court overturned prior common law precedent established in Roe v. Wade (1973), illustrating how common law evolves through judicial reinterpretation.
Frequently asked questions
Common law relies on binding judicial precedent and case-by-case development, while civil law systems are organized around comprehensive statutory codes that judges apply but do not formally extend through binding precedent.
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