Common law
The common lawso named because it was "common" to all the king's courts across Englandoriginated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Common law
The centuries-old authority of the common law courts in England to develop law case by case and to apply statute law—"legislating from the bench"— is a traditional function of courts, which was carried over into the U.S. system as an essential component of the "judicial power" specified by Article III of the U.S. constitution. Justice Oliver Wendell Holmes, Jr. summarized centuries of history in 1917, "judges do and must legislate” (in the federal courts, only interstitially, in state courts, to the full limits of common law adjudicatory authority).