Old Russian Law or Russian Law is a legal system in Kievan Rus' (since the 9th century), in later Old Rus' states (knyazhestva, or princedoms in the period of feudal fragmentation), in Grand Duchy of Lithuania and in Moscow Rus' (see: Grand Duchy of Moscow and Tsardom of Russia). Main source was Old Slavic customary law: Zakon Russkiy (Law of Rus') (it was partly written in ). Another sources were Old Scandinavian customary law (see: Varangians) and Byzantine law (since the 10th century).
The main written sources were Russkaya Pravda ("Russian Justice") (since the 11th century) and Statutes of Lithuania (since the 16th century).
According to Old Russian chronicles, in 862, Slavs and Finns invited Varangians under the leadership of prince Rurik to rule in their land:
They said to themselves, "Let us seek a prince who may rule over us and judge us according to the Law." They accordingly went overseas to the Varangian Russes: these particular Varangians were known as Russes, just as some are called Swedes, and others Normans, English, and Gotlanders, for they were thus named. The Chuds, the Slavs, the Krivichians, and the Ves' then said to the people of Rus', "Our land is great and rich, but there is no order in it. Come to rule and reign over us."
Early Russian state settled on the oral treaty, or "ryad" (Old Russian: рядъ) between the prince (knyaz) with his armed force (druzhina) on the one hand, and tribal "nobility" and formally all people on the other hand. The prince and his druzhina defended people, decide lawsuits, provided trade and built towns. And people paid tribute and took part in irregular military. During the ensuing centuries the ryad was playing an important role in Old Russian princedoms: the prince and his administration (druzhina) found their relationship with people ("all land", "all townsmen" in Old Russian chronicles) on the treaty. A breach of the treaty could result in exile of the prince (Izyaslav Yaroslavich and Vsevolod Yaroslavich) or even in murder of the prince (Igor Rurikovich and Igor Olgovich).