Yoro ritsuryo code (code promulgated in the Yoro period) Sagi-ritsu (rules against falsity) prescribes that the person who made a statement different from the fact in the preparation of an imperial decree or soji (reports to be submitted to the emperor through Daijokan [Grand Council of State]) and josho (letters and/or documents to be submitted to the emperor) is sentenced 2-year imprisonment, and also it is stated as one of serious crimes in "Hossoshiyosho" (The Essentials for the Judiciary) (a legal book compiled by the Sakanoue clan between the end of Heian period and the early Kamakura period) which describes the kugeho (court noble law, laws issued by the imperial court) at the end of Heian period.
養老律令詐偽律には、詔の作成や奏事・上書において事実と異なることを行った者を徒罪2年とするとされ、平安時代末期の公家法を伝える『法曹至要抄』でも重罪の1つとして説かれている。