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. Prior to the Norman Conquest, much of England's legal business took place in the local folk courts of its various shires and hundreds. A variety of other individual courts also existed across the land: urban boroughs and merchant fairs held their own courts, as did the universities of Oxford and Cambridge, and large landholders also held their own manorial and seigniorial courts as needed. Additionally, the Catholic Church operated its own court system that adjudicated issues of canon law.
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).