High Court of Australia recognises constitutional power to legislate with respect to same-sex marriage

The Commonwealth v Australian Capital Territory [2013] HCA 55


The High Court of Australia has held that a law recognising same-sex marriage in the Australian Capital Territory was inconsistent with Commonwealth legislation and therefore was invalid. The High Court also stated unanimously that the Commonwealth has the power to legislate with respect to marriage equality pursuant to s51(xxi) of the Constitution (the marriage power).


On 22 October 2013, the ACT Legislative Assembly passed the Marriage Equality (Same-Sex) Act 2013(ACT) (the ACT Act). The purpose of this legislation was to recognise marriage equality within the ACT

The Commonwealth filed a writ against the ACT, arguing (amongst other things) that the Marriage Equality Act was inconsistent, in whole or in part, with the Marriage Act 1961 (Cth) (the Marriage Act) 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 Commonwealth contended that the 2004 amendments to the Marriage Act, which defined marriage as being "between a man and a woman", made it clear that the Commonwealth intended to legislate on the subject of marriage and only meant to recognise marriage between heterosexual couples. The Commonwealth also submitted that it was unnecessary for the Court to determine the scope of the marriage power.

Australian Marriage Equality sought, and was granted, leave to intervene as amicus curiae in support of the ACT. AME intervened in support of the ACT but also to argue that the Court was required to determine the scope of the marriage power. AME’s submissions addressed in detail the reasons why the marriage power should be interpreted to encompass same-sex unions.

The decision

The High Court found in favour of the Commonwealth in a unanimous judgment and declared the ACT Act to be invalid and of no effect. 

The court held that the ACT Act was inconsistent with the Marriage Act. There was no need to determine whether the ACT Act was also inconsistent with the Family Law Act 1975 (Cth), as contended by the Commonwealth.

Critical to the majority's reasoning was the emphasis in the ACT Act on equality. The ACT Act's intention was to confer on same-sex marriage a status equal to that of marriage under the Marriage Act, and it was this feature of the ACT Act that meant it could not operate concurrently with the Marriage Act. This finding was particularly reliant on the 2004 amendments to the Marriage Act, which meant that same-sex marriages could not be recognised at the Commonwealth level. Significantly, the objects clause and other provisions focussed on by the Court were the very provisions that AME and its legal team had previously sought to persuade the ACT Government to amend.

The majority further noted that there were many similarities between ACT Act and the Marriage Act in relation to eligibility to marry, recognition of marriages, the ceremonial requirements to solemnise a marriage, provisions around void marriages and requirements to terminate a marriage. These similarities supported the finding by the court that the intention of the ACT Act was to intrude on the area of law regulated by the Marriage Act, being marriage laws which only recognised heterosexual couples. The majority relevantly stated (at [60]) that "By providing for marriage equality, the ACT Act seeks to operate within the same domain of juristic classification as the Marriage Act".

Importantly, the majority also stated that section 51(xxi) of the Constitution (the power to make laws with respect to marriage) could be used to legislate for marriage equality. By defining thenotion of marriage recognised by section 51(xxi) not as a concept frozen in time at Federation, but as a "topic of juristic classification" that will shift according to the passage of time, the court rejected the contention that marriage (pursuant to section 51(xxi)) can only be between a man and a woman according to the definition in Hyde v Hyde(1866) LR 1 P & D 130.

Consequently, the court stated (at [33]) that:

…"Marriage" is to be understood in s 51(xxi) of the Constitution as referring 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.

With respect to marriage equality, the court stated (at [37]) that:

Other legal systems now provide for marriage between persons of the same sex. This may properly be described as being a recent development of the law of marriage in those jurisdictions. It is not useful or relevant for this Court to examine how or why this has happened. What matters is that the juristic concept of marriage (the concept to which s 51(xxi) refers) embraces such unions. They are consensual unions of the kind which has been described. The legal status of marriage, like any legal status, applies to only some persons within a jurisdiction. The boundaries of the class of persons who have that legal status are set by law and those boundaries are not immutable.


Although the High Court invalidated the ACT Act, the decision confirmed a pathway forward for the recognition of marriage equality in Australia in the future. In this regard, there are several aspects of the decision that merit further comment.

First, the High Court's unequivocal endorsement of the proposition that the marriage power extends to same-sex marriage removes any barriers to the Commonwealth legislating to recognise marriage equality in the future. This was a fantastic outcome for AME and an important victory for the marriage equality movement.

Secondly, the decision emphasises that Commonwealth legislation is the appropriate vehicle to recognise marriage equality. Specifically, the court noted (at [1]) that: "under the Constitution and federal law as it now stands, whether same sex marriage should be provided for by law (as majority of the Territory Legislative Assembly decided) is a matter for the federal Parliament".

However, it is important to note that the High Court did not expressly rule out the possibility of any further state or territory legislation in favour of same-sex marriage. The High Court focussed on the flaws in the ACT Act, principal among which was that the ACT Act failed to sufficiently distinguish the status conferred upon the relationship and the subject matter dealt with in the legislation from the corresponding provisions in the Marriage Act. This leaves open the possibility of other states and territories successfully defending their own marriage equality legislation.

Trieste Corby and Chris Travers are Lawyers with Allens.

Note: Together with the HRLC, Trieste Corby and Malcolm Stephens from Allens represented Australian Marriage Equality in relation to its intervention in this matter. Counsel for AME were Jeremy Kirk SC and Perry Herzfeld. The HRLC has been providing on-going legal support for AME in relation to constitutional questions surrounding State and Federal marriage laws including instructing Bret Walker SC, Chris Young and Perry Herzfeld to prepare a number of legal opinions and negotiating with the ACT Government in relation to amendments to their marriage laws. To see Australian Marriage Equality’s written submissions to the High Court in this case, click here.