The problem with identities is that they’re like … elbows. Everybody has them. And like elbows on an aeroplane armrest, they sometimes battle to occupy the very same space. That is the essence of a case in the NSW Federal Court this week.

Tickle v Giggle isn’t the light-hearted affair the litigants’ names would suggest. Giggle is an app created to provide a space for women to communicate on a range of issues just among women. It is a platform to find other women to travel with, share houses with, and, if they’re lesbian, perhaps find someone to date.

Roxanne Tickle says Giggle for Girls illegally discriminated on the grounds of gender identity after her access to the app was revoked.Credit: AAP

Trans men, who were born female, are invited to join the app, which sees itself as providing a safe space for all people who have experiences and vulnerabilities particular to female biology.

Roxanne Tickle is a trans woman who was excluded from partaking in the app because, while she identifies as a woman, she was born male. Tickle has reportedly had gender-affirming surgery and, as Australian law allows, changed her birth certificate to reflect her gender identity. Her lawyer has taken pains to emphasise how genuinely and profoundly she feels that she is a woman. Despite these feelings, Tickle was denied access to Giggle, on the basis that the app is exclusively for biological females, which Tickle is not.

The court case will decide whether Tickle was discriminated against by Giggle. But the deeper question this case raises pertains to a conflict of rights. The same conflict of rights that inspired Harry Potter author JK Rowling’s challenge to a new Scottish law which, opponents feared, would make it a hate crime to draw the distinction between women by biology and women by identification.

The question these cases raise is whether biological women have a right to an identity distinct from trans women. To date, trans rights activists have assumed that there is no conflict and that the way they feel about womanhood is the way every woman must feel. However, many biological women feel that their distinct identity is being erased by a gender-based concept of womanhood.

This creates a conflict of rights, which occurs when two (or more) parties have rights that can’t be exercised simultaneously. Two elbows can occupy the same armrest if one is content to angle a bit forward and the other a bit back, but they can’t both occupy the position that feels most natural at once.

A less flippant example is abortion: from the moment a woman conceives, there is a potential conflict of rights between her and the child she is carrying. Abortion laws mediate this conflict of rights on a sliding scale, which is why a first-trimester abortion is unconditionally the decision of the woman in Australia, while a third-trimester abortion is only likely to be approved in extreme circumstances. These are what we call zero-sum situations: only one party can fully exercise their rights; the other has to give way.