This is a short piece of text, but it is the central point in the history.Source:
https://lib.sale/pravo-grajdanskoe-uchebnik/osobyie-poryadki-nasledstva-nasledovanie-47524.html

The inheritance of peasants is determined according to their customs. IX т., Особ. прил., Общ. крест. пол. 38. Пол. Вык. 166. Местн. Велик. 110. Местн. Малор. 93. Местн. Закавк., ст. 81. Местн. Бессар., ст. 36.The rule is applied irrespective of, whether the inheritance is a part of the peasant plot or other property and whether the inheritance case is in the volost or general courts.

MY COMMENT: in 1828-1856 in Russia 91 % of the population were peasants. The same was both in Europe, and in colonies, except for cities-ports. So that 91 % of the population followed the law, fixed nowhere, with rare exception, being not related to the city law. Lawyers de facto in general bypass this question and it is the right decision, — the village followed ancient laws like Lex Salica and Rus’ Justice of 11th century origin. In the middle of 19th century of the village did not need any changes – their life was the same as 800 years ago.

I mean that the English case law in colonies (including the USA) could be valid only in case of large trading companies. In remote places the developed forms of law were useless: a microscope and a calliper in a rural blacksmith shop were of no use.

THE BASIC IDEA
I declare: at least until 1848 the rural Customer Law worked for 90 % of the world population and thus had nothing in common to the law forms dominating in modern history textbooks.