As the Kamakura period began, in addition to the currently existing laws and ordinances of the dynasty (the Imperial court and Court nobles), such as court noble law and honjo law (a law to govern manor in the medieval Japan), the newly established Kamakura bakufu instituted Samurai laws which was unique to samurai families by collecting legal precedents after the inauguration of MINAMOTO no Yoritomo, the udaisho (Major Captain of the Right Division of Inner Palace Guards) family, and formulating Goseibai-shikimoku (code of conduct for samurai).
鎌倉時代に入ると、従来から存在した王朝（朝廷・公家）の法令（公家法・本所法など）以外にも新たに登場した鎌倉幕府によって、右大将家（源頼朝）以来の判例の蓄積や御成敗式目の成立など、武家固有の法令（武家法）が構築されていった。