The Wealth of Nations by Part 3 Chapter 4 Page 10

proprietor, where all the inhabitants were armed and accustomed to stand by one another, would have cost the king, had he attempted it by his own authority, almost the same effort as to extinguish a civil war. He was, therefore, obliged to abandon the administration of justice through the greater part of the country to those who were capable of administering it; and for the same reason to leave the command of the country militia to those whom that militia would obey.

It is a mistake to imagine that those territorial jurisdictions took their origin from the feudal law. Not only the highest jurisdictions both civil and criminal, but the power of levying troops, of coining money, and even that of making bye-laws for the government of their own people, were all rights possessed allodially by the great proprietors of land