Excluding women from some rodeo events because they may not be strong enough is "just one of those things", the industry body says.
But the Human Rights Commission says the stance may be unlawful.
On Monday, The Press featured 15-year-old rising rodeo star Libby Bent, the only female to compete in the steer-riding competitions at the Canterbury Rodeo in Mandeville, North Canterbury, last weekend.
For Bent to graduate to the senior ranks and be able to ride bulls at the rodeo next year, she will have to change a longstanding rule - that women cannot ride in rough-stock events.
New Zealand Rodeo Cowboys Association administration director Fred Doherty said women could compete in three of the seven rodeo events but were forbidden to enter the rough-stock events "because that's the way it has always been".
"I am fairly sure there is nowhere in the world where women compete against men in rough-stock events," he said.
"Females generally lack the upper-body strength needed, and it's just one of those things . . .
"The rule is based on tradition. It came from the fact that it has always been there."
Doherty did not believe excluding women from rough-stock events was discriminatory because rodeos also held the female-only barrel-racing event.
"Barrel racing is a ladies-only event and you don't see any guys kicking up about that," he said.
A Human Rights Commission spokeswoman said the rodeo rules might breach the Human Rights Act.
"On the face of it, the competition may [breach the act], but in the absence of a complaint and full details of the competition, the commission is unable to comment any further," she said.
Doherty said for the rodeo rule to be overturned, someone would have to put in a remit at the next annual meeting, and the association's members would need to vote in its favour.
Women can apply for dispensation to compete in a rodeo's rough-stock event, but Doherty was aware of only one such case.
A woman was granted dispensation to compete about six years ago, but "when the time came, she ran out of nerve and decided it wasn't for her after all", he said.
- The Press