After MINAMOTO no Yoritomo died, an administrative system was created by the Hojo clan to fill the role of Shogunal advisor to the Imperial Court; they also arranged the system so that even if Yoritomo's bloodline died out, the Kamakura bakufu system could continue, and to serve as the bakufu's legal basis created the Goseibei Shikimoku (Formulary of Adjudications), the first set of laws governing the warrior class, which was to became the legal foundation of medieval society in Japan.
源頼朝の死後、将軍の輔弼制度として北条氏による執政制度も創設され、たとえ頼朝の血統が絶えても鎌倉幕府体制は永続するように制度整備がなされ、その裏打ちとして御成敗式目という初の武家法が制定され、その後の中世社会の基本法典となった。