In Australia, the Commonwealth and State governments are authorised to exercise power that is neither conferred by legislation nor expressly provided for in a constitution: non-statutory executive power. Where non-statutory executive power is exercised, questions arise as to the role of the courts in keeping the government accountable for this action. Although intermediate appellate courts at the Commonwealth and State levels have applied the House of Lords’ decision in Council for Civil Service Unions v Minister for the Civil Service to permit judicial review of non-statutory action in an appropriate case, it is unclear what cases are “appropriate” and how the traditional grounds of review and remedies might apply to action that is not authorised by legislation. Dr Sapienza’s ground-breaking book attempts to bring clarity to this area of law by assessing the extent to which Australian judicial review principles are capable of application to an exercise of non-statutory executive power. It begins by categorising non-statutory executive power according to the manner in which an exercise of it is capable of having a legal effect. It then examines each element of judicial review – jurisdiction, justiciability, grounds of review, standing and remedies – to determine which aspects of each element are likely to pose an obstacle to a successful judicial review application in respect of each category of non-statutory action. In so doing, it lays a conceptual and doctrinal foundation from which legal practitioners and the courts can navigate this complex area of law on a case-by-case basis, as they are increasingly being called on to do. As the first treatise to thoroughly explore this area, it is an invaluable resource for governments and those advising them. It will also be the starting point for lawyers seeking to challenge an exercise of non-statutory executive power as well as for the courts they call upon to review the action.