The use of unstated rules of recognition. [fact]
The use of unstated rules of recognition, by courts and others, in identifying particular rules of the system is characteristic of the internal point of view. Those who use them in this way thereby manifest their own acceptance of them as guiding rules and with this attitude there goes a characteristic vocabulary different from the natural expressions of the external point of view.
H. L. A Hart, The Concept of Law, loc. 326