Customary law was until recent times part of the legal system in place almost everywhere in the Muslim world, especially, although not only, outside the cities. Even nowadays it is a significant force in many areas. The various customary legal systems have their roots in the period before conversion to Islam, and their survival has led Muslim jurists to develop a variety of techniques, both practical and doctrinal, for dealing with them. The way in which these customary legal systems work is here illustrated by examples from North Africa, the Middle East, the Caucasus, Central Asia, the Indian subcontinent, and Indonesia. This part of the article analyzes historical development of legal custom in the Northeast Caucasus from the pre-modern times to nowadays.