NZ First wants to copy the UK in defining ‘woman'. It makes no legal or human sense

The Spinoff

22-04-2025

In a swift importation of global culture wars, NZ First has introduced a new member's bill. Paul Thistoll explains why it's ill-conceived on a number of levels.
Last week, the UK Supreme Court ruled that, for the purposes of the Equality Act, 'woman' means biological woman. The decision, welcomed by anti-trans campaigners around the world, including here in New Zealand, might make sense within Britain's particular statutory framework, but politically, morally, and sociologically — and yes, even scientifically — the ruling is deeply flawed. It also has minimal legal relevance to Aotearoa.
Despite that, New Zealand First has this week proposed legislation through a Jenny Marcroft member's bill that would seek to 'protect the term 'woman' in law'. The bill appears to be entirely inspired by the UK decision, and proposes that 'woman' be defined in law as an 'adult human biological female' and 'man' as an 'adult human biological male'.
In the UK, the judgement is the latest expression of a global backlash against the inclusion of trans people in public life. But we should be clear-eyed: this ruling cannot be imported into our system without flattening our unique legal, cultural and human rights landscape.
A judgement built on exclusion
The case concerned the interpretation of the word 'woman' under the UK's Equality Act 2010. In essence, the Court found that the term referred to a biological female, and that a trans woman with a gender recognition certificate could be lawfully excluded from single-sex spaces, such as women's support services. The implications of this decision are significant: it entrenches biological essentialism into the heart of UK anti-discrimination law.
Perhaps most tellingly, no trans voices were permitted to intervene in the hearing. The judgement proceeds in a vacuum, disconnected from the people most affected. This absence is not neutral. It helps explain why the Court treated biology as the sole and stable marker of identity. But identity is not reducible to chromosomes.
Moreover, the UK system itself is highly different from ours. In the UK, individuals can follow a medicalised, bureaucratic process under the UK Gender Recognition Act 2004 to gain a certificate which states their desired gender. This is in stark contrast to Aotearoa, where sex self-ID is the implemented paradigm (interestingly, it was Tracey Martin of NZ First who shepherded those reforms through parliament).
In their haste to get this divisive bill into the biscuit tin, NZ First have given absolutely no thought to how the laws that would rely on this definition would be enforced. As I wrote to Judith Collins last year (on the matter of sports), the regime that NZ First proposes would be entirely unimplementable. It would require compulsory chromosomal testing and the establishment of a sex-passport infrastructure. I wrote: 'They are simply not serious options in a free society… and compulsory chromosomal testing of newborns… could give rise to another parliamentary occupation.' Lex non cogit ad impossibilia – The law does not compel the impossible.
Aotearoa has a different human rights framework
The UK decision has no binding effect in Aotearoa, and it should have no persuasive authority either. We have a different legislative framework, different institutions and different Treaty obligations.
New Zealand's Births, Deaths, Marriages, and Relationships Registration Act 2021 allows individuals to self-identify their sex on their birth certificate without medical intervention. This reflects a recognition that self-identification is consistent with the dignity and autonomy of trans people. It also reflects the understanding that gender identity, not biology, is what matters in ensuring equal access to rights and services.
Our courts have already shown a more nuanced understanding of gender in several cases. In Muir v Police, which involved a transgender woman who was stopped and questioned by police for cross-dressing, the High Court acknowledged that a person's gender identity was relevant to how they should be treated in police custody, suggesting our judiciary recognises that gender identity, not just biological sex, has legal significance.
Many have argued that our Human Rights Act 1993 should explicitly include gender identity, gender expression, and variations of sex characteristics. But even in its current form, it has been interpreted to include trans people. The Human Rights Commission's chief legal officer, Hannah Northover, recently confirmed to me that the Commission still relies on the 2006 Crown Law advice, which found that discrimination against trans people falls within the existing sex discrimination provisions.
We are not Britain. Our legal direction is different by design.
Aotearoa has a different social and political context
What's often overlooked in these discussions is just how different our social context is from Britain's. We've already had transgender representation at the highest levels of government, with Georgina Beyer making history as the world's first openly transgender MP back in 1999 – more than two decades before the UK elected its first.
Our political landscape hasn't been captured by anti-trans bigotry to the same extent as Britain's, as much as one minor party might try. The loudest transphobic voices in our public discourse represent a small minority, and most feminist organisations and leaders in Aotearoa maintain inclusive stances that recognise trans women as women – it's only a particularly vocal fringe that aligns with trans-exclusionary positions.
The political reality here also offers structural protections. Any attempt to legislate similar restrictions would face significant obstacles, given the likelihood of coalition governments under MMP and the staunch support of gender diversity from the likes of the Green Party and Te Pāti Māori.
Inclusion works. Exclusion harms.
The main effect of the UK judgement will be to exclude people with Y chromosomes from female-only spaces. But the safety of those spaces is not derived from chromosomes. In Aotearoa, Women's Refuge is explicitly trans-inclusive. They understand that safety comes from trust, support and shared experience — not from anatomy.
Trans women are not a threat to women's safety. That narrative is both false and harmful. There is no evidence that trans inclusion in single-sex spaces leads to harm. But there is overwhelming evidence that exclusion harms trans people: increasing isolation, vulnerability and barriers to essential services.
The UK judgement also erases intersex and non-binary people entirely. It offers no space for those whose bodies or identities don't align with binary definitions. It doubles down on a model of sex that is neither inclusive nor scientifically accurate.
Rights are grounded in gender, not biology
The judgement's essential mistake is to treat biology as the bedrock of human rights. But rights are grounded in how people live, how they are perceived and how they are treated. Gender is what drives discrimination. Gender is what shapes experience. And gender is what must underpin human rights protections.
Trans women experience misogyny as women. They are excluded as women. Their safety, dignity, and freedom depend on being recognised as women. If the law fails to protect them on that basis, then it is the law that is failing.
The judgement opens the door to a resurgence of biological essentialism — a framework that has been used for centuries to exclude, marginalise, and punish those who do not conform. It is a politics of control masquerading as neutrality.
Gender diversity has deep roots in Aotearoa
It's also historically inaccurate to treat gender fluidity as some modern or imported concept. In pre-colonial Māori society, gender was understood as more expansive than Western colonial norms. Elizabeth Kerekere's research on takatāpui affirms the presence and value of diverse gender identities within traditional Māori communities. These identities were not only accepted, but integrated into social and cultural life.
The imposition of rigid, binary gender norms was a colonial act. To now re-impose those definitions through the back door of the law would be to compound that harm. It would risk breaching Te Tiriti o Waitangi, and would be susceptible to challenge on that basis.
Any future attempt to import UK-style reasoning into New Zealand law would need to reckon with these histories and obligations.
We deserve better
The UK Supreme Court's ruling might make sense within its own narrow legal logic, but it does not make sense here. Aotearoa has a chance to lead with clarity: to affirm that human rights are for all of us, including trans, intersex, and non-binary people, and to reject the idea that biology determines worth. We need to build a legal culture rooted in dignity, autonomy, and inclusion.
Should NZ First's member's bill to define 'woman' in strictly biological terms be pulled from the biscuit tin and progress, Peters and his party will have an almighty fight on their hands. Aotearoa is not a country gripped by anti-trans hysteria, no matter how hard some try to import it. Most people here still believe in dignity, decency, and letting others live in peace.
We should treat the UK decision as a warning, not a precedent.