This chapter reviews the modern cases on the ‘third source’ in England and Wales and around the Commonwealth. This review illustrates that the law is fundamentally uncertain on the legal nature and exact provenance of these powers within each jurisdiction surveyed. It also illustrates that basic questions of legal theory relating to official empowerment and official action are unavoidable in the context of non-statutory executive powers. This demonstrates the gap between theory and practice in a specific context and justifies the need for the basic and wide-ranging interrogation of the law of judicial review undertaken in the book.

This chapter sets out the taxonomy of non-statutory executive powers ultimately adopted. It is a very simple taxonomy that draws a fundamental distinction between statutory and non-statutory executive powers but no distinctions for the purposes of judicial review between non-statutory executive powers associated with the Royal Prerogative and those that are more mundane, and appear to be nothing more than the ‘residual liberties’ of the Crown as a legal person. Once the logic of office, official empowerment, and official action is adopted as a premise, the idea of the ‘third source’ as generally articulated simply falls away. While the distinction may be interesting or useful in a historical sense, it is of no relevance to the ‘how’ or ‘why’ of judicial review.

This chapter introduces the problem of official action beyond statute as a central concern to public law theory. It reviews the most important classical accounts of the Royal Prerogative and the modern notion of a ‘third source’ of executive power besides statute and prerogative. It also introduces a major them in the book, namely the concept of ‘official power’ as a set of ‘legal powers’ and uses this critically to assess common misconceptions about the nature of official action beyond statute – particularly conceptions of the third source as a set of ‘residual liberties’ inuring in the Crown in common with private individuals.