There were two main origins of the Honjo law: one was in a legal structure that had governed the influential families called honjo, which owned Shomuken (the authority of the jurisdiction and the administration of Shoen), and the other was the common law in Shoen that became approved by the honjo.
本所法には、荘務権を有する本所と称される権門が属する法体系に根源を持つものと荘園内部における慣習法が本所に容認されたものがある。