There are basic principles of Australian constitutional law which must be understood by anyone who analyses or discusses matters relating to the Constitution and decisions of the High Court.
The Australian Constitution Act 1900 contains 9 clauses. Covering clause 9 contains " The Constitution ". The Constitution is a document of 128 sections which is primarily about conferring power on three organs of government. The legislature or law making body is Parliament which consists of the House of Representatives, the Senate and the Governor-General (as the Queen's Representative) the Executive (the Prime-Minister and Cabinet exercising actual power which is legally vested in the Governor-General as the Queen's Representative) and the Courts of law. The Constitution also establishes the federal system and a very significant part of the Constitution is devoted to allocation of powers to the Commonwealth and the States.
The High Court is the final interpreter of the Constitution. Clause 5 of the Australian Constitution Act 1900 requires the High Court to act in accordance with the Constitution and the law. However, given that the High Court is the final arbiter of what the Constitution says, the Constitution is ultimately what the High Court says it is. There is no appeal against decisions of the High Court which are patently contrary to the words of the Constitution or its spirit.
Where the Commonwealth Parliament enacts legislation, there are two essential pre-requisites. First, there must be a section, or part of a section of the Constitution which confers authority to enact the act. The words of a proposed law must be capable of being fitted within a section or a part of a section of the Constitution which gives the Commonwealth Parliament the power to legislate in the particular area. If there is no such power, the proposed law is invalid.
Secondly, the proposed law, even if it falls within a head of power, must not offend a prohibition in the Constitution. Section 92 of the Constitution enacts:
"trade, commerce and intercourse among the several States shall be absolutely free".
This placed a restriction on the power of Commonwealth and State Parliaments. This was the clear intention of the draftsmen. If it was intended to exempt the Commonwealth the Constitution would have said so. However, the High Court in the exercise of its infallible authority to interpret the Constitution, held, in effect, that the provision limits only the States.