Yassa

Yassa (alternatively: Yasa, Yasaq, Jazag, Zasag, Mongolian: Их засаг, Yehe Zasag) was a secret written code of law created by Genghis Khan. It was the principal law under the Mongol Empire even though no copies were made available. Most of this law was supervised by Genghis Khan himself and his stepbrother Shihihutag who was then high judge (in Mongolian: улсын их заргач) of Mongol Empire. Genghis Khan appointed his harshest son Chagatai (later Chagatai Khan) to oversee the execution of it. It is unclear if it was not made secret once generally not followed. The original Yassa seems to have been issued in the form of decrees which also were issued in wartime in regard of the opposition to the Mongols (it appears that Chinggis Khan still saw them, by symbols used on the standards, as the Mengwu Shiwei of the time of Wang Mang)including in the cities, "biliqs"/"biliks".