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In Cth v ACT  HCA 55, the Commonwealth of Australia challenged the validity of a law of the Australian Capital Territory (ACT) that purported to legislate for same-sex marriage. The Commonwealth argued the ACT law was inconsistent with the Commonwealth law on marriage, most notably the Commonwealth Marriage Act 1961. To determine the validity of the ACT law, the High Court first had to decide the meaning of "marriage" under section 51(xxi) of the Australian Constitution.
Was "marriage" fixed to the meaning marriage had at in 1901, when the Australian colonies federated under the Australian Constitution?
At federation, "marriage" was understood to have the meaning given to it by several nineteenth century English cases. According to the law of England back then, a marriage was a union between a man and a woman on the same basis as Christian marriage, namely:
(1) a voluntary union,
(2) for life,
(3) of one man and one woman,
(4) to the exclusion of all others.
If "marriage" still means "one man and one woman", then the Commonwealth Parliament would not have the power to legislate with respect to same-sex marriage and the ACT law could not be inconsistent with the Commonwealth law. — there would be no valid Commonwealth law for the ACT law to offend. The High Court held unaminously that "marriage" was not confined to its 1901 meaning and that marriage could extend to same-sex marriage. Some people, especially the religious right, have decried the Court's departure from the "traditional" or Christian meaning of marriage.
Yet, as the High Court itself has said, the secular meaning of marriage had departed from the Christian meaning of marriage even before 1901. For example, one of the elements of a Christian marriage (listed above) was the voluntary union of a man and a woman for life. But even by 1901, a marriage could be dissolved by a civil court. In civil law, "marriage" no longer meant "marriage for life".
Also, the Christian elements "of one man and one woman to the exclusion of all others" no longer necessarily apply to a valid civil marriage, either. English and Australian law now recognise polygamous marriages for many purposes. For example, section 6 of the Commonwealth Family Law Act 1975 says:
"For the purpose of proceedings under this Act, a union in the nature of a marriage which is, or has at any time been, polygamous, being a union entered into in a place outside Australia, shall be deemed to be a marriage."
If the "for life" element of marriage has been taken away, and the monogamous element of marriage has been taken away, then why not also take away the gender element?
Thus, the legal meaning of marriage is nowadays much broader than the Christian meaning of marriage. For the purposes of section 51(xxi) of the Australian Constitution, "marriage" means a consensual union formed between natural persons in accordance with legally prescribed requirements that the law recognises as intended to endure and be terminable only in accordance with law and a union to which the law accords a status affecting and defining mutual rights and obligations. The Commonwealth Parliament can prescribe the unions to be regarded as "marriages". And in section 51(xxi) of the Constitution, "marriage", as expressly and unanimously stated by the High Court, is a word that includes a marriage between people of the same sex.
For present purposes, the High Court case shows how a word can change its meaning over time (lots of words have changed their meaning). The case also shows how a meaning of a word depends on context. In the Christian context, marriage may mean one thing; in the secular context, marriage may mean something different. It is important for people to keep those contexts separate. Australians do not live under a Christian State, or a Muslim State, or a Jewish State, or under the laws of any religion. Australians live under a secular State; thus, the secular meaning of marriage, as defined by the highest court in the land, rules us — all of us.
But for thousands of Australians, the debate about the meaning of "marriage" is much more important than just the history, evolution, and meaning of a word. The word "marriage" accords a legal status. That status, in turn, defines people's rights and obligations. The status, "married", is currently denied to same-sex couples in Australia. Despite constant claims to the contrary peddled by the religious right in Australia, denying that status to same-sex couples creates inequality and injustice.
When you are accorded the status of "marriage" or of being "married", you are automatically accorded a bundle of rights and obligations under State and Territory and Commonwealth laws. For example, in NSW, a will is automatically revoked on the "marriage" of the person who made the will. In the same jurisdiction, if your "spouse" invests your money without your consent, you can apply to recover your money. The rights and obligations that "marriage" accords are not trivial. Recently, a gay man's plea to see his partner's deceased body was denied; he was told he was not the dead man's next of kin because they were not "married".
So, words matter. The word "marriage" matters, in particular.
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