Yasan.

1722 P. Aubin tr. F. Pétis de la Croix Hist. Genghizcan i. vi. 79 After the Salutations they began to read the Yassa... The Laws in the Mogul Language are called Yassa, and sometimes Yasac.

1929 V. A. Riasanovsky Customary Law of Mongol Tribes i. ii. 21 Jenghiz-Ḵhan..established some fundamental rules and punishments and put all this down in a book which he called ‘Yassa’, also called ‘Yassak’, but the proper name is Yassa.

1930 D. S. Mirsky tr. Vladimirtsov Life Chingis-Khan vii. 74 Chingis-Khan made use of the newly-introduced alphabet for the purpose of committing to writing his Sayings (Bilik) and his Institutions (Jasak, Yasak, or Yasa).

1946 G. Stimpson Bk. about Thousand Things 125 The Mongols were very much afraid of thunder and the provision in the Yassa may have been designed to prevent them from throwing themselves into lakes and rivers during a storm.

1953 O. Caroe Soviet Empire xiv. 239 There are two strains in the spiritual inheritance of Turkistan, the first the Yasa or Yasak, the Turkish tribal tradition, and the second the Sheriat, the sacred law of Islam.

1974 Encycl. Brit. Macropædia IX. 857/2 Hülagü Khan..had..the yāsā of Genghis Khan to apply as the law of the Mongol state.

1990 Economist 3 Mar. 6/4 Genghis Khan did indeed devise and promulgate a comprehensive series of civil, criminal, military and..commercial laws. These, the yasa, were the basis for law in much of Asia for over 600 years.