Organisers of the 'Defy Definition' protests estimated more than 10,000 people marched across five New Zealand cities on 14 June 2026, opposing NZ First's member's bill to write biological definitions of 'woman' and 'man' into law.

The Legislation (Definitions of Woman and Man) Amendment Bill, introduced by NZ First, would add new definitions to New Zealand legislation: 'woman' as 'an adult human biological female' and 'man' as 'an adult human biological male'. The bill is currently before a select committee — essentially a parliamentary subcommittee — and is open to public submissions. Auckland saw the largest single-city turnout, according to NZ Herald reporting from 12 June.

Protest organisers say the bill would erase transgender people from legal recognition. They've committed to campaigning against it until it's defeated, according to RNZ. This gets at the heart of the dispute: whether anchoring 'woman' and 'man' to biological sex removes meaningful legal recognition for people whose gender identity differs from the sex they were assigned at birth.

NZ First's supporters argue the opposite. They contend that New Zealand law currently uses 'woman' and 'man' without consistency or clear biological grounding, creating practical problems in areas like single-sex service provision and sports eligibility rules. Critics counter that embedding biological sex as the single legal definition will flow through to the rights and protections that transgender New Zealanders currently rely on.

Member's bills like this move through Parliament slowly. The bill will complete its select committee hearings — including the current public submission phase — before any second reading debate. The maths in the House right now means the bill's fate isn't predetermined. NZ First holds the bill but needs coalition partners to get it across the line; National and ACT have not publicly committed to supporting it as written.

The street turnout is significant by recent New Zealand standards. Organiser estimates and actual crowd counts often differ, though, and no independent head-count has been released. What stands out is that the bill has already triggered organised, sustained opposition well before Parliament votes on it — a pressure point that will likely shape how coalition parties weigh the political cost of their positions as the select committee process plays out.

Public submissions on the bill remain open, giving both sides a formal parliamentary channel alongside street action.