1. Law is a union of primary and secondary rules.
2. A primary rule is one that imposes an obligation or a duty.
3. A rule is said to impose an obligation or a duty when the demand for conformity is insistent and the social pressure brought to bear upon those who deviate is great.
4. A secondary rule is one that confers a power of introduces/changes/modifies primary rules.
5. There are three types of secondary rules: the rule of change, the rule of adjudication and the rule of recognition.
6. The rule of recognition is the ultimate criterion for validity in a legal system. A rule is legally valid and therefore law, if it conforms to the requirements set forth in the rule of recognition.
7. The rule of recognition itself can neither be valid nor invalid. The proof of its existene is in the fact of its acceptance.
8. There are two ways of looking at rules: the external point of view and the internal point of view. The external point of view merely analyses the convergence of habit and behaviour. The internal point of view looks at rules as standards governing behaviour, and endorses them.
9. For a legal system to exist, it is a sufficient condition that citizens take an external point of view towards primary rules; and a necessary condition that officials take the internal point of view towards secondary rules.
10. The rules of a legal system are ascertainable, yet in certain 'penumbral' cases - are indeterminate. In such cases, judicial discretion is necessary.