When Kamakura bakufu (Japanese feudal government headed by a shogun) was formed, there was no statutory law yet; however, it did not follow the ritsuryo law or the kugeho (laws issued by the Imperial Court) and the trials were held according to orders and precedents of morals which had been practiced by samurai since the birth of samurai.
鎌倉幕府成立時には成文法が存在しておらず、表向き律令法・公家法には拠らず、武士の成立以来の武士の実践道徳を「道理」として道理・先例を基づく裁判をしてきたとされる。