Cooper v Commissioner of Income Tax for the State of Queensland

The appellant, the Chief Justice of the Supreme Court of Queensland, appealed to the High Court of Australia against a decision of the Supreme Court of Queensland. The dispute concerned the Commissioner of Income Tax for Queensland's claim for income tax on the appellant's judicial salary. The appellant contended that taxing his salary was repugnant to the Queensland Constitution and therefore invalid.

The High Court was required to determine whether the Queensland Parliament had the legislative power to impose income tax on the salaries of Supreme Court Judges, notwithstanding provisions in the Queensland Constitution that appeared to protect such salaries from diminution. Specifically, the Court had to consider whether the Income Tax (Consolidated) Acts 1902-1904 and the Income Tax Declaratory Act 1905 were validly enacted or if they were inconsistent with the constitutional framework governing the State.

The Court reasoned that the Queensland Constitution, as established by the Order in Council of 1859 and subsequently consolidated in the Constitution Act 1867, imposed limitations on the legislative powers of the Queensland Parliament. It held that any law inconsistent with the Constitution was invalid unless the Constitution itself was first altered through a direct legislative process. The Court found that section 17 of the Constitution Act 1867, which stipulated that judicial salaries "shall in all time coming be paid and payable... so long as the patents or commissions... shall continue and remain in force," effectively prohibited any reduction or diminution of a Judge's salary during their term of office. Therefore, the imposition of income tax on judicial salaries constituted such a diminution and was beyond the legislative competence of the Queensland Parliament without a prior amendment to the Constitution.

The High Court affirmed the decision of the Supreme Court of Queensland, holding that the Income Tax Acts, in so far as they purported to tax the salaries of Supreme Court Judges, were inoperative due to their inconsistency with the Queensland Constitution.