The paper features Mongolian law in context of its interaction with common law of Mongolian tribes of pre-state period, traditions of Mongolian society under Genghis Khan rule, and as part of the Qing dynasty. The main aspect of the research is the legal basis and acts enforced on the modern territory of Inner Mongolia. On the basis of the materials of Russian and foreign researchers unknown to awide academic community, the author identifies six groups of sources of Mongolian Law and providesdetailed characteristics of each. The first group of sources incorporates Yassa as a source of rules and punishments for violating them. The second group of sources represents the so called secondary legal acts enabling to perform administration and other administrative actions including decrees (tchzan) and orders (tchi) of the Great Khan, labels, defters and pajtsze. The third group of sources comprises the laws of the the Yuan dynasty (1271-1368) and North Yuan (1368-1691); the fourthincluded Oirat charters (Tsaadzhin-bichik), decrees of Oiratean khans and petroglyphs. The fifth groupof the Mongolian sources included Khalha acts in particular the great semikhoshunn law and Khalkha Jirum. Group six of the sources involves Chinese Law for Mongolia approved after Khalkha and SouthMongolia were included in the Qing dynasty. On the basis of detailed analysis and comparison, theauthor matches the sources and their separate norms, which forms a conclusion that the process ofthe development of Mongolian law differed from the one of neighbor states and even after the loss ofsovereignty, public relations on the territory of Mongolian lands were ruled by special normative acts.