The Commonwealth v ACT [2013] HCA 55: The Landmark Same Sex Marriage Australia Case

Case Overview at a Glance

Introduction: Why This Case Still Matters

Few cases in Australian constitutional law have captured the public imagination as vividly as The Commonwealth v ACT [2013] HCA 55. Decided on 12 December 2013 by a unanimous six-judge panel, this ruling sits at the crossroads of constitutional interpretation, federal-territory legislative power, human rights advocacy, and the long road to same sex marriage in Australia. Though the High Court ultimately struck down the ACT's law, the decision planted a constitutional seed that would eventually blossom into the nationwide legalisation of same gender marriage in Australia in December 2017.

For law students, legal practitioners, and anyone curious about the legal history of same sex marriage in Australia, this case is essential reading. It answered foundational questions about what 'marriage' means under the Australian Constitution, who holds the power to define it, and what limits apply to territory legislatures when comprehensive federal law already occupies a field.

Background: The Political and Legal Context

The Marriage Act Australia and the 2004 Amendment

The primary federal statute governing matrimonial unions in Australia is the Marriage Act 1961 (Cth) - commonly referred to as the Marriage Act Australia. Originally enacted to provide a uniform national framework for marriage ceremonies and registration, the Marriage Act 1961 was, for most of its history, silent on whether marriage was exclusively a heterosexual institution.

That silence was ended by the Marriage Amendment Act 2004 (Cth), which inserted a definition of marriage as 'the union of a man and a woman to the exclusion of all others, voluntarily entered into for life.' This amendment directly responded to fears that Australian courts might be compelled to recognise same-sex marriages solemnised overseas. The 2004 amendment became the central statutory battleground in Commonwealth v ACT - the High Court would later treat it as a comprehensive and exhaustive statement of federal intent, leaving no room for concurrent territory legislation.

The ACT Moves First: The Marriage Equality (Same Sex) Act 2013

Against a backdrop of growing public support for marriage equality across Australia, the Australian Capital Territory Legislative Assembly passed the Marriage Equality (Same Sex) Act 2013 (ACT) on 22 October 2013. The Act commenced on 7 November 2013, with the first weddings held from 7 December 2013. Its primary purpose was 'to provide for marriage equality by allowing for marriage between two adults of the same sex.'

To avoid a direct clash with federal law, the ACT's drafters defined 'marriage' as '(a) the union of 2 people of the same sex to the exclusion of all others, voluntarily entered into for life; but (b) does not include marriage within the meaning of the Marriage Act 1961 (Cwlth).' In other words, the ACT argued it was creating a different, complementary legal institution - not a competing one.

The Commonwealth's Challenge

Commonwealth Attorney-General George Brandis announced in October 2013 that the federal government would challenge the ACT law if passed. The Commonwealth filed a writ arguing the Marriage Equality Act was inconsistent, in whole or in part, with both the Marriage Act 1961 (Cth) and the Family Law Act 1975 (Cth) within the meaning of section 28(1) of the Australian Capital Territory (Self-Government) Act 1988 (Cth). The matter was expedited. The Court reserved judgment for 10 days, during which 31 same-sex couples married under the ACT legislation - marriages that would later be voided by the Court's ruling.

The Legal Issues Before the Court

The High Court was asked: Is the Marriage Equality (Same Sex) Act 2013, enacted by the Legislative Assembly for the Australian Capital Territory, inconsistent with either or both of two Acts of the federal Parliament: the Marriage Act 1961 and the Family Law Act 1975?

Answering this required the Court to first resolve a foundational constitutional question: does the Commonwealth's marriage power under s 51(xxi) of the Constitution extend to same sex marriage? If it did not, there might be space for territory legislation. If it did, the federal field was occupied.

The Amicus Curiae Brief

Australian Marriage Equality Inc filed an amicus curiae brief supporting the Commonwealth's position - an unusual alliance. A marriage equality advocacy group effectively argued that only Parliament (not a territory) could legislate for same sex marriage. This reflected strategic legal thinking: a broad constitutional ruling on the marriage power would open the door for federal reform, which ultimately proved correct.

The High Court's Decision and Reasoning

The Scope of 'Marriage' Under s 51(xxi)

The Court held that 'marriage' in s 51(xxi) of the Constitution refers to a consensual union formed between natural persons in accordance with legally prescribed requirements which is not only a union the law recognises as intended to endure and be terminable only in accordance with law but also a union to which the law accords a status affecting and defining mutual rights and obligations.

Crucially, the Court declined to freeze the constitutional meaning of 'marriage' at its common-law definition at federation. It held unanimously that the marriage power in s 51(xxi) is broad enough to encompass same sex marriage - confirming that the federal Parliament had always possessed the constitutional capacity to legislate for marriage equality without any referendum.

The Marriage Act as a Comprehensive Code

The Court held that the Marriage Act 1961 is a comprehensive and exhaustive statement of the law of marriage. The High Court found in the 2004 amendments an 'implicit negative proposition that the kind of marriage provided for by the Marriage Act 1961 (Cth) is the only kind of marriage that may be formed or recognised in Australia.'

Why the ACT's Definitional Strategy Failed

The ACT had argued ingeniously that there was no inconsistency because its Act explicitly excluded unions 'within the meaning of the Marriage Act 1961 (Cwlth)' from its own definition. The two laws, the ACT contended, operated in parallel streams that never collided. The High Court rejected this. While the federal Parliament 'has not made a law permitting same sex marriage,' the absence of such a law 'does not mean that the Territory legislature may make such a provision' and 'does not mean that a Territory law permitting same sex marriage can operate concurrently with the federal law.'

The Final Orders

The Court declared unanimously that the whole of the Marriage Equality (Same Sex) Act 2013 (ACT) was of no effect. Because the ACT Act did not validly provide for the formation of same sex marriages, its provisions about the rights of parties to such marriages and the dissolution of such marriages also could not have separate operation. The 31 same-sex marriages that had been performed under the ACT legislation were consequently voided.

The Road from 2013 to 2017: How Australia Legalised Same Sex Marriage

The Australian Marriage Law Postal Survey

After the High Court's ruling, the campaign for marriage equality intensified. The Coalition government arranged for the Australian Bureau of Statistics to conduct the Australian Marriage Law Postal Survey between 12 September and 7 November 2017. The results: 7,817,247 (61.6%) responding Yes and 4,873,987 (38.4%) responding No, with 79.5% of eligible Australians participating. All states and territories recorded a majority Yes response.

The Marriage Amendment (Definition and Religious Freedoms) Act 2017

On 9 December 2017, the Marriage Act 1961 was updated to allow for marriage equality. The Act now defines marriage as 'the union of 2 people to the exclusion of all others, voluntarily entered into for life.' The first same-sex wedding under Australian law was held on 15 December 2017. Overseas same-sex marriages were immediately recognised.

Key Legal Principles Established

• Living Constitutional Interpretation: The meaning of 'marriage' in the Constitution is not frozen at federation and can evolve to encompass same-sex unions.
• Federal Paramountcy: The Marriage Act 1961, as amended in 2004, occupied the entire field of matrimonial law under s 109 of the Constitution.
• Covering the Field Doctrine: Federal legislation so comprehensive that no territory can pass concurrent laws even on topics the federal Parliament has not explicitly addressed.
• Courts Do Not Make Social Policy: A unanimous panel stressed that 'The only issue which this Court can decide is a legal issue,' emphasising judicial restraint.

Frequently Asked Questions

What was The Commonwealth v ACT case about?

It was a High Court challenge by the federal government against the ACT's Marriage Equality (Same Sex) Act 2013, which purported to allow same-sex couples to marry in the Australian Capital Territory. The High Court struck the law down as inconsistent with the federal Marriage Act 1961.

Did the High Court say same sex marriage is unconstitutional in Australia?

No - the opposite. The Court ruled unanimously that the marriage power under s 51(xxi) of the Constitution is broad enough to allow Parliament to legislate for same sex marriage. It was the ACT territory law that was struck down; only the federal Parliament can legislate on the subject.

When did same sex marriage become legal in Australia?

Same sex marriage became legal across all of Australia on 9 December 2017, following the Marriage Amendment (Definition and Religious Freedoms) Act 2017.

What happened to the 31 couples who married under the ACT law?

Their marriages were voided by the High Court's decision. The couples had married in the brief window between 7 and 12 December 2013.

Conclusion

The Commonwealth v ACT [2013] HCA 55 is far more than a case about a struck-down territory law. It is the constitutional cornerstone of same sex marriage law in Australia - the case that confirmed Parliament had always possessed the power to legislate for marriage equality, and that the only obstacle was political will. When that will was expressed in December 2017 following the postal survey, Australia joined the growing community of nations recognising the equal dignity of all marriages. Understanding this case means understanding how Australian constitutional law, federal-territory relations, and the long campaign for same gender marriage in Australia converged in one extraordinary December week in 2013.