The Common Law and the Monarchy
I like to ask my Torts students what judges use as their authority for making common-law decisions. The answer is a statute. Every state has a law that either adopts the common law of England as of July 4, 1776 or the common law as developed when the state was a territory. In this sense, all common-law is statutory interpretation.
You can make a related point about the Crown. The source of Elizabeth II’s right to reign is the Act of Settlement (enacted in 1701), which was designed to resolve the succession after the childless Queen Anne died. Among other things, it bars any Catholic from being the monarch. Thus, the Queen is really nothing more than the head of an administrative agency with a special religious test attached and without the Chevron deference.