As a judge, jay applies common law rules. these rules develop from

The rules developed from decisions of the courts in legal disputes
Common law is used to handles the cases that had already been previously handled by the court.
If,  the case had never been handled and would influence the well being of large number of people, the case would be forwarded to the Supreme court.

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.