Outline of Argument for a High Court Challenge to the Full Federal Court Ruling in “Giggle v Tickle”

The central vulnerability of the Full Federal Court's ruling in Giggle for Girls Pty Ltd v Tickle [2026] FCAFC 64 lies precisely here: the statutory silence of the Sex Discrimination Act 1984 (Cth) (SDA) on the meaning of "sex."

By failing to define "sex" explicitly, the Act has invited the judiciary to assume the role of philosopher and linguist. When Justice Bromwich at first instance declared that "in its contemporary ordinary meaning, sex is changeable," and the Full Court (Justices Perry, Abraham and Kennett) upheld this expansive, multi-factorial view on 15 May 2026, the courts did not merely interpret the law, they constructed a novel framework untethered from the statute's text, context, and history.

A successful High Court challenge must eschew cultural polemics and rest on strict statutory construction, constitutional limits, and the internal logical incoherence of treating an unamended foundational legal category ("sex") as fluid.

Ground 1: The Principle of Statutory Contemporanea Expositio

The strongest ground centres on text, context, and legislative purpose at enactment.

When Parliament passed the SDA in 1984, "sex" had a clear, settled meaning in ordinary language and law: the biological distinction between male and female based on reproductive function. This was no accident. The Act was enacted to implement Australia's obligations under the Convention on the Elimination of All Forms of Discrimination against Women (CEDAW), which addresses discrimination rooted in biological sex and women's reproductive capacity.

The Dynamic Interpretation Error

The Federal Court adopted a "living statute" approach, treating the ordinary meaning of "sex" as having evolved to encompass legal and social recognition of gender identity. Yet the High Court has repeatedly held that, while the application of statutory language may adapt to new circumstances, its essential meaning is fixed by reference to the time of enactment unless Parliament amends it.

The Argument: Parliament in 1984 anchored the SDA in the external affairs power (s 51(xxix) of the Constitution) to protect biological women from sex-based discrimination. To reinterpret "sex" as changeable detaches the Act from its constitutional foundation and original purpose. Judicially updating a core term in this way exceeds legitimate interpretation and enters the realm of legislative amendment.

Ground 2: The 2013 Amendments Embody Structural Redundancy

A fundamental canon of construction is that Parliament does not legislate in vain. In 2013, the Gillard Government amended the SDA to insert "gender identity" as a separate protected attribute, defined in s 4 as:

"the gender-related identity, appearance or mannerisms or other gender-related characteristics of a person (whether by way of medical intervention or not) with or without regard to the person's designated sex at birth."

Crucially, Parliament left "sex" entirely unamended. It also repealed the former biological definitions of "man" and "woman" that had appeared in the original Act.

[1984 Foundation] ──> "Sex" (biological male/female, tied to CEDAW and reproductive reality)

│

[2013 Amendment]──> "Gender Identity" added as a SEPARATE, distinct protected attribute

│

[2026 Court Ruling]──> Merged the two by treating "Sex" as including social/gender identity elements

The Incoherence of Fusion

By holding that "sex" itself is non-binary, socially constructed, and changeable (including via state-issued documents and self-identification), the Full Court erased the deliberate statutory boundary Parliament created. If "sex" already encompassed gender identity and social recognition, the 2013 insertion of a separate "gender identity" ground was legally redundant, a result courts must strive to avoid.

The High Court should restore the two distinct categories Parliament enacted:

1.An objective, biological baseline ("sex").

2.A subjective, psychological and social expression ("gender identity").

Collapsing the former into the latter renders the 2013 amendments surplusage and undermines the Act's architecture.

Ground 3: The Internal Philosophical and Legal Incoherence of "Changeable Sex"

If "sex" is a multi-factorial, fluid concept determined by social interaction, self-identification, and administrative paperwork, the law collapses into conceptual instability.

Category Collapse

Direct sex discrimination requires a stable comparator: less favourable treatment than a person of the opposite sex. A non-binary, shifting spectrum makes identification of a reliable comparator logically and practically impossible. The definition renders "woman" circular: a woman is anyone legally or socially recognised as a woman. A statute built on tautology cannot deliver the predictable boundaries required for single-sex services, sports, or safety provisions. This offends the rule of law's demand for certainty.

Ground 4: The Misapplication of "Special Measures"

Section 7D of the SDA permits "special measures" to achieve substantive equality between men and women. Giggle contended that restricting the app to biological females was a valid special measure to create a safe space addressing systemic online harassment and safety concerns faced by women.

The Full Court rejected this, holding that because Tickle is legally a woman, exclusion could not constitute a measure addressing inequality between the sexes and instead amounted to direct discrimination (including on appearance/gender-related characteristics).

The Structural Flaw: This reasoning creates a paradox. The moment a biological male obtains a modified birth certificate or asserts gender identity, biological females lose the ability to invoke s 7D to maintain single-sex spaces. The exception is swallowed by the redefined category, rendering s 7D largely toothless for its intended beneficiaries.

Conclusion: The Task for the High Court

The High Court of Australia is a court of legalism, not social policy. The central submission must be straightforward: the judiciary exceeded its constitutional role.

If the meaning of "sex" is to be decoupled from biological reality — a change with profound implications for women's rights, single-sex spaces, sports, and the protective purpose of the SDA — that shift must be expressly debated and enacted by the Federal Parliament. It cannot be read into forty-year-old statutory silence by judicial redefinition of a foundational term.

Until Parliament amends the Act, "sex" must remain anchored in its original biological meaning. Otherwise, the entire architecture of the Sex Discrimination Act risks collapsing into incoherence and unpredictability.