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.
Legal origins theory
While English common law originated in thirteenth century England and has then been transplanted through colonization and occupation to England’s ex-colonies (United States, Canada, Australia, and several countries in Central America, Africa and Asia), the Scandinavian common law was developed in Denmark and Sweden and the German common law sprang in Germany and Switzerland [Guerriero 2016a, p. 54]. These last four countries then exported their common law model to the respective colonies or to those jurisdictions (China, Greece, Japan, Romania, South Korea, Taiwan, Thailand, and Turkey), which were never colonized but borrowed their initial legal order from the European codes considered most advanced at the time [Guerriero 2016a, p. 54]. Civil law instead has its roots in Roman law, was incorporated by the Napoleonic codes first and then by both the Austrian and Russian Civil codes, and has been then introduced via mainly colonization and occupation into continental Europe, the Near East, Latin America, Africa, and Indochina. Bulgaria, Ethiopia, Iran, and Kazakhstan instead purposely borrowed their initial legal order from either France, Russia, or England [Guerriero 2016a, p. 54].