Why do English and French courts work so differently?

English and French courts differ because the two traditions disagree about where law comes from. In the common law of England, law is primarily developed through judicial decisions rather than statutes. It is called "common" because it was common to all the king's courts of England, growing from their practices after the Norman Conquest of 1066. In the civil law tradition used in France, the primary source is a legal code, written down in advance: civil law systems are characterised by their reliance on codes.

France's code has a human story. Before the Napoleonic Code, France did not have a single set of laws; law consisted mainly of local customs, notably the Custom of Paris. In 1804 a commission drafted one code for everyone, and Napoleon chaired 55 of its 107 plenary sessions. The Revolutionaries had come to take a negative view of judges making law, and the Code's article 5 prohibited judges from deciding a case by laying down a general rule: making general rules is for legislators, not judges.

The styles of trial differ too. Common law courts usually use an adversarial system, with two sides presenting their cases to a neutral judge. In civil law systems, criminal cases usually follow an inquisitorial system, where an examining magistrate develops the evidence during the investigation.

Neither is a minority taste. Civil law is the world's most common legal system, practised in about 150 countries, and about a third of the world's population lives under common law or a mix of the two. Louisiana, for instance, is the only US state whose private law rests heavily on French and Spanish codes.