When Goseibai-shikimoku (code of conduct for samurai) was establshed during the Kamakura period, it was explicitly written in Taibon sankajo (three basic rights of shugo, provincial constable) that obanyaku was a post to be assumed by gokenin (an immediate vassal of the shogunate in the Kamakura and Muromachi through Edo periods).
鎌倉時代の武家法である御成敗式目が制定されると、大犯三ヶ条において御家人の職務として明文化された。