Legal recognition of relationships: marriage, de facto and same-sex: HSC Legal Studies

What this dot point is asking

In the Legal Studies Stage 6 Syllabus (2009) Family option, students learn about legal requirements of marriage and alternative family relationships, and must be able to outline the legal requirements of a valid marriage. Recognition of same-sex relationships is one of the four contemporary issues that must be studied, and you must be able to evaluate the effectiveness of legal and non-legal responses to it.

This page gives you the marriage rules, the law on de facto and registered relationships, and the history of same-sex recognition, which is one of the best case studies for the themes of changing community values and law reform (see 2025 HSC Question 27(b)).

The answer

The legal requirements of a valid marriage

Marriage is a Commonwealth matter (Constitution s 51(xxi)). The Marriage Act 1961 (Cth) sets uniform rules for the whole country.

1. Definition

Marriage means "the union of 2 people to the exclusion of all others, voluntarily entered into for life" (s 5(1)). This replaced "the union of a man and a woman" from 9 December 2017.

2. Marriageable age

Both parties must be 18 (s 11). A person aged 16 or 17 may marry a person aged 18 or over only if a judge or magistrate authorises it because the circumstances are exceptional and unusual (s 12), and a parent or guardian consents (s 13). Two people under 18 can never marry each other.

3. Void marriages

Under s 23B a marriage is void (treated as never having existed) if:

• either party is already married to someone else (bigamy is also an offence under s 94, maximum 5 years);
• the parties are in a prohibited relationship: ancestor and descendant, or brother and sister, including half-siblings and relationships by adoption (cousins may marry);
• the marriage was not solemnised in accordance with the law of the place where it took place;
• consent was not real, because it was obtained by duress or fraud, a party was mistaken about the identity of the other party or the nature of the ceremony, or a party was mentally incapable of understanding the nature and effect of the ceremony;
• either party was not of marriageable age.

A court can declare a marriage void by a decree of nullity (Family Law Act 1975 (Cth) s 51). Nullity is rare because divorce is available on a no-fault basis.

4. Formalities.

• A Notice of Intended Marriage must be given to the celebrant at least one month (and no more than 18 months) before the wedding (s 42).
• The marriage must be solemnised by an authorised celebrant: a minister of religion of a recognised denomination, a state officer, or a Commonwealth-registered marriage celebrant.
• There must be two witnesses aged 18 or over (s 44).
• Civil celebrants must use the prescribed words, and the parties must say vows in which each takes the other as their lawful wedded spouse (s 45).
• The marriage is then registered with the state registry of births, deaths and marriages.

Forced marriage

Consent is the heart of marriage, so the law criminalises forced marriage. The Crimes Legislation Amendment (Slavery, Slavery-like Conditions and People Trafficking) Act 2013 (Cth) inserted forced marriage offences into the Criminal Code (Cth):

• a marriage is forced if a party enters it without freely and fully consenting because of coercion, threat or deception, or because they are incapable of understanding the nature and effect of the ceremony (s 270.7A);
• causing a person to enter a forced marriage, or being a party to one, is an offence (s 270.7B), with a maximum of 7 years imprisonment, or 9 years if aggravated, for example where the victim is under 18 (s 270.8);
• since 2015 a person under 16 is presumed incapable of understanding the nature and effect of a marriage ceremony (s 270.7A(4)).

Forced marriage mainly affects young women, and prosecutions are rare because victims are often reluctant to give evidence against family members. Non-legal responses matter: the Australian Federal Police, the Support for Trafficked People Program and NGOs such as Anti-Slavery Australia provide support and education.

Alternative family relationships

De facto relationships. Under s 4AA of the Family Law Act 1975 (Cth) a person is in a de facto relationship with another person if they are not legally married to each other, are not related by family, and, having regard to all the circumstances, have a relationship as a couple living together on a genuine domestic basis. The circumstances include:

• the duration of the relationship and whether they share a residence;
• whether a sexual relationship exists;
• financial dependence or interdependence and ownership of property;
• mutual commitment to a shared life, care of children and public reputation;
• whether the relationship is registered.

A de facto relationship can exist between two people of the same sex, and even if one of them is legally married to someone else or in another de facto relationship (s 4AA(5)).

Property claims. Since 1 March 2009 (1 July 2010 in South Australia), de facto couples outside WA have access to the Family Law Act property and maintenance regime (Part VIIIAB). A court can make orders if (s 90SB):

• the relationship lasted at least 2 years in total; or
• there is a child of the relationship; or
• the relationship is or was registered under state law; or
• one party made substantial contributions and serious injustice would result if no order were made.

Applications must be made within 2 years of separation (s 44(5)). Couples who do not qualify may still use the Property (Relationships) Act 1984 (NSW), which also covers close personal relationships, such as two adults living together where one provides domestic support and personal care to the other.

Registered relationships. Every state except Western Australia, and the ACT, allows couples to register their relationship, giving easy proof of its existence (WA and the Northern Territory have no relationship register):

In NSW both parties must be adults, at least one must live in NSW, and neither can be married or in another registered relationship. A registered relationship can be revoked by application.

Polygamous and overseas marriages. Polygamous marriages cannot be entered into in Australia, but a polygamous union entered into overseas is treated as a marriage for Family Law Act proceedings (s 6), so the parties can seek divorce, property and parenting orders. Overseas same-sex marriages have been recognised in Australia since 9 December 2017.

Recognition of same-sex relationships (contemporary issue)

This issue shows law reform responding, slowly, to changing community values.

Decriminalisation

Male homosexual acts were criminal in every state. NSW decriminalised them in 1984. Tasmania was last, in 1997, after the UN Human Rights Committee found in Toonen v Australia (1994) that its law breached the right to privacy under the International Covenant on Civil and Political Rights, and the Commonwealth passed the Human Rights (Sexual Conduct) Act 1994 (Cth). NSW has allowed historical convictions to be extinguished since 2014.

De facto recognition

The Property (Relationships) Legislation Amendment Act 1999 (NSW) extended NSW de facto law to same-sex couples. The Same-Sex Relationships (Equal Treatment in Commonwealth Laws - General Law Reform) Act 2008 (Cth) and related 2008 Acts removed discrimination against same-sex couples and their children in about 85 Commonwealth laws, including superannuation, tax, social security and the Family Law Act.

Resistance to marriage

The Marriage Amendment Act 2004 (Cth) inserted the definition "the union of a man and a woman" and prevented recognition of overseas same-sex marriages. The Civil Unions Act 2006 (ACT) was disallowed by the Governor-General on the Commonwealth's advice in June 2006. The ACT's Marriage Equality (Same Sex) Act 2013 (ACT) was struck down in Commonwealth v Australian Capital Territory (2013) 250 CLR 441: the Marriage Act 1961 (Cth) was a complete statement of the law of marriage, so the ACT law was inconsistent under the self-government legislation. Importantly, the High Court also held that the word "marriage" in s 51(xxi) of the Constitution is broad enough to include same-sex marriage, so only federal legislation was needed.

Marriage equality

The Australian Marriage Law Postal Survey (September to November 2017) returned 61.6% Yes on a 79.5% participation rate. It was a voluntary, non-binding survey run by the ABS, not a referendum or plebiscite. Parliament passed the Marriage Amendment (Definition and Religious Freedoms) Act 2017 (Cth), which commenced on 9 December 2017. It:

• changed the definition to "the union of 2 people";
• recognised overseas same-sex marriages;
• allowed ministers of religion (s 47) and new "religious marriage celebrants" (s 39DD) to refuse to solemnise marriages, and bodies established for religious purposes to refuse facilities, goods or services for a marriage on religious grounds (s 47B).

In 2025, 4,636 marriages were registered for couples of the same or non-binary gender, about 3.9% of all marriages (ABS).

Related recognition. The Sex Discrimination Amendment (Sexual Orientation, Gender Identity and Intersex Status) Act 2013 (Cth) made discrimination on these grounds unlawful. Since 1 July 2025, people in NSW can change the sex recorded on their birth certificate without surgery (Equality Legislation Amendment (LGBTIQA+) Act 2024 (NSW)), bringing NSW into line with most other states.

Evaluating the law

Judgement. The law recognising relationships is now largely effective: it offers clear marriage rules, recognises de facto and registered relationships and treats same-sex couples equally. Its weaknesses are that reform came slowly, sometimes against the courts' reading of the Constitution, and that some protections (forced marriage) depend on victims who find it hard to use them.

In one sentence

The Marriage Act 1961 (Cth) sets uniform rules for a valid marriage (age 18, real consent, not already married or closely related, proper formalities), the Family Law Act and state registers recognise de facto and registered relationships, and same-sex relationships moved from criminalisation to marriage equality in 2017, showing the law responding, slowly but substantially, to changing community values.

Try this

Q1. Outline the circumstances in which a marriage is void. (4 marks)

• What the marker wants. The five s 23B grounds with brief explanation.

Q2. Explain the role of the High Court in the recognition of same-sex relationships. (5 marks)

• What the marker wants. Commonwealth v ACT (2013): inconsistency invalidated the ACT Act, but the marriage power includes same-sex marriage, so Parliament could legislate.

Q3. To what extent has law reform achieved just outcomes for same-sex couples? (8 marks)

• What the marker wants. The reform timeline with statutes and dates, the survey and 2017 Act, remaining tensions over religious exemptions, and a clear judgement.