Implied powers are powers necessary for the performance of the function entrusted to an inferior court or tribunal by statute, but the power of implication only applies in the absence of express words or a reasonably plain intention to the contrary.

'Necessary' in the context of implied powers refers to what is reasonably required or legally ancillary to accomplishment of express powers, subjected to the touchstone of reasonableness and whether implication is 'proper', and does not extend to what is 'merely desirable or useful' or 'convenient or profitable'.

When assessing what is necessary for exercise of express jurisdiction and power, the function exercised must be regarded as a continuous process, not confined to determination of the particular case, so the question must be answered by reference to what is necessary to protect the tribunal's ability to function into the future.

The express provisions and limitations of the Industrial Relations Act 1979 (WA) regulating the Board must assume importance in determining what is 'necessary'.

When Parliament explicitly gives a power by a particular provision which prescribes the mode in which it shall be exercised and the conditions and restrictions which must be observed, it excludes the operation of general expressions in the same instrument which might otherwise have been relied upon for the same power (doctrine of express statutory language excluding implied alternatives).

Where special provisions in legislation are intended exhaustively to govern their particular subject matter, general or implied provisions that would encroach on that subject matter will not apply (repugnancy doctrine).

Section 80L of the Industrial Relations Act 1979 (WA), which expressly lists certain Commission powers that apply to the Board, operates to exclude by omission powers not listed, particularly where other constituent authorities are expressly granted broader application of Part II powers.

The omission of section 33 from section 80L, when Parliament deliberately chose to include it for other constituent authorities, is a plain indication of legislative intention to exclude the ability to summon witnesses from the Board's powers.

A witness summons deprived of enforceability loses its key characteristic of compulsive force and ceases to serve its necessary purpose, becoming no different to a voluntary request.

The enforcement mechanism in section 84A of the Industrial Relations Act 1979 (WA) applies only to contraventions of 'any provision of this Act', meaning expressly provided sections, and would not apply to a summons issued under an implied power.

The regulatory power under section 80K(4) to regulate the Board's own procedure is a power to regulate the procedure which the Board follows in exercising its substantive powers and jurisdiction, not a power that itself confers substantive power or jurisdiction to issue a witness summons.

There is no scope within settled principles of statutory construction to regard lack of controversy about a statutory provision or practice as informing the statutory construction exercise.