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. (october 2007)
yassa (alternatively: yasa, yasaq, jazag, zasag, mongolian: Их засаг, ikh zasag) is/was the forty millenary oral law code of the mongols declared in public in bokhara by genghis khan de facto law of the mongol empire even though the "law" was kept secret and never made public. the yassa seems to have its origin as decrees issued in war times. later, these decrees were codified and expanded to include cultural and life-style conventions. by keeping the yassa secret, the decrees could be modified and used selectively. it is believed that the yassa was supervised by genghis khan himself and his stepbrother shihihutag who was then high judge (in mongolian: улсын их заргач) of the mongol empire. genghis khan appointed his second son chagatai (later chagatai khan) to oversee the execution of the laws.