Judicial review is commonly assumed to be available solely in respect of the exercise of power that may be described as ‘public’. Until recently, Australian courts have been of the view that the source of a power would be determinative of whether the power was public in the requisite sense: only power which derived from statute or the prerogative would be public for the purposes of judicial review.

That view, however, is beginning to change. Over the last two decades, and beginning with the seminal Court of Appeal decision in R v Panel on Take-overs and Mergers, Ex parte Datafin, the English courts have moved away from relying exclusively on the source of power as determinative of whether that power is public. Rather, power that does not derive from statute or the prerogative may nonetheless be public, and therefore amenable to the court's review jurisdiction, if it may be determined to be public by virtue of its nature or character. This notion that power may be public as a result of its nature is of increasing significance for judicial review in Australia. The notion is of most immediate relevance in the context of the review jurisdiction that the state Supreme Courts were granted upon being established, and which mirrored the jurisdiction possessed at the time by the superior courts at Westminster.