One of the sources of law is unusual: law made by judges, one case at a time. That is the common law, and it is the reason American lawyers spend so much time reading old cases.
Key idea
The common law grew from the decisions of English royal judges, case by case, and the United States inherited it. Civil law systems, in much of Europe and Latin America, start instead from comprehensive written codes. Louisiana's private law draws on the civil law tradition.
Why it works
In the 1100s, King Henry II sent royal judges around England to hear disputes. They decided cases by the customs and earlier decisions of the king's courts, and because the same judges met and compared notes, a law common to the whole kingdom grew up. Each decision became a reason for deciding the next like case the same way. William Blackstone's Commentaries on the Laws of England (1765–1769) organized that law into a system, and American lawyers learned from it. After independence, most states passed reception statutes adopting English common law as of a set date, so far as it fit American conditions. Louisiana, shaped by French and Spanish rule before the 1803 purchase, built its private law on a civil code instead.
| Common law tradition | Civil law tradition | |
|---|---|---|
| Starting point | decided cases, plus statutes | a comprehensive code, plus statutes |
| Role of past decisions | formally binding (stare decisis) | influential, but formally the code governs |
| Judges' opinions | long, signed, with dissents | often shorter, focused on the code's articles |
| Where found | England, the United States (except Louisiana private law), Canada (except Quebec), Australia, India | France, Germany, Spain, most of Latin America, Japan, Quebec |
Worked example: Where does the rule come from?
A court must decide whether a store owner owes a duty of care to a customer who slipped on a wet floor. No statute addresses it. Where does the court look?
- No statute or regulation speaks, so the court looks to the common law of torts.
- It reads earlier decisions of its own state's courts on store owners and customers.
- It applies the rule those cases set, adjusting for any new facts.
Answer: To precedent: the state's common law of negligence, built from earlier cases.
Worked example: When a statute speaks
Later, the state legislature passes a statute on store owners' duties. Does the common law still control?
- Statutes outrank judge-made common law.
- Where the statute speaks, it controls; where it is silent, the common law fills the gaps.
- Courts still interpret the statute, and their readings become precedent too.
Answer: No: the statute controls where it applies; the common law fills the gaps.
Common mistake
Thinking civil law systems ignore past cases and common law systems ignore statutes. Both use codes and cases. Much American law is now in statutes (criminal codes, the Uniform Commercial Code), and judges in civil law countries do read and follow earlier decisions. The difference is emphasis and the formal weight given to precedent. And do not confuse the civil law tradition (codes) with civil cases (non-criminal suits): same word, different meaning.
This is an educational course, not legal advice.