The Commonwealth or the Minister shall not exercise the powers (including discretions) of the Commonwealth or of the Minister, as the case may be, under this Act or under a relevant revenue - sharing agreement in a way that would:
(a) discriminate between States or parts of States within the meaning of paragraph 51(ii) of the Constitution; or
(b) give preference to one State or any part thereof over another State or any part thereof within the meaning of section 99 of the Constitution.