The ability to do all things ‘necessary or convenient’ for performing statutory functions is a common mechanism for ensuring powers are adequate for their intended role12. The court (at [105-107]) sets out basic principles for giving content to powers of this kind. They are ‘strictly ancillary’, do not extend the scope of provisions, are tied to the specific powers and functions conferred13, and are not freestanding.
Having a supplemental character, the correct starting point for determining their content must be the underlying powers and functions. iTip – starting with what ‘necessary or convenient’ may mean in other contexts is the wrong way to go.
This case is from Episode 49 of interpretationNOW!
12 Shanahan  HCA 4 (at -), Pearce & Argument Ch 14.
13 Anthony Lagoon (1987) 15 FCR 565 (at 585) cited.