Scouts New Zealand and other groups say they are disappointed that victims of abuse in their communities won't be heard by the Royal Commission into Historical Abuse.
They said the newly released terms of reference drew a number of arbitrary lines that excluded people in sports groups, as well as young people jailed in adult prisons.
The government announced this week that the Royal Commission would be the biggest inquiry ever undertaken in New Zealand, but in a statement from the commission, the members said they needed to consult lawyers on just who is included.
Scouts New Zealand chief executive Joshua Tabor said he was disappointed his organisation missed out.
"From our perspective it is a lost opportunity around shaping and giving voice to young people and those victims and survivors of sexual assault have a story to tell and want to be heard," he said.
He said the Australian Royal Commission was very successful - having a narrow definition of sexual abuse, but a wide definition of institutions, while New Zealand's approach mirrors what was used in the UK - which wasn't nearly as effective.
The terms of reference are much longer and complicated than those used in Australia's inquiry, and psychologist Michelle Mulvihill, who was a consultant there, said the New Zealand terms of reference had the wrong focus.
"The terms of reference seem to be written from the perspective of understanding perpetrators, not victims," she said.
"They've kind of turned it upside down I think, and that's unfortunate."
Ms Mulvihill was a member of the professional standards committee of the St John of God Brothers for nine years, which looked at child sexual abuse cases - including the Marylands case in Canterbury, where one brother was guilty of 16 counts and faced another 33 charges.
She said it was good news the New Zealand Government responded to feedback and broadened the inquiry to include faith-based organisations.
But she said the terms of reference were vague even when referring to the churches, such as whether abuse outside the church premises would be included.
She said all victims needed assurances that they would be heard.
"And the prime minister said that, in the press release it says 'you will be included'," she said.
"But then you read section 17 and it kind of says 'maybe'. 'You will be included... maybe'."
But some community groups still have hope they may be eventually be included.
Joshua Tabor from the Scouts said he wouldn't be surprised if the terms were expanded as more victims come forward.
"It's hard to give two groups of people a voice in a reconciliation process and exclude a third and fourth group of people based on the arbitrariness of where they sit," he said.
"Either the youth development or sporting sector, I mean that just seems like a haphazard approach."
But the sporting sector is not rushing to be included.
Sport New Zealand chief executive Peter Miskimmin said his organisation was undertaking a "wide-ranging review" that included child protection, but he confirmed it would not be reaching back to look at historic cases.
He said he hoped people who had been abused would come forward, but it wasn't in his mandate to facilitate that.
"That is not up for us to do," he said.
"I can only go by what we've been given the mandate to do. Any opportunity where people who have a grievance of the past that want to bring those forward I would support, but I can only deal with what we're dealing with here."
The terms also exclude any abuse after 1999 - though the commission does have discretion.
The terms do include people abused in juvenile detention, as well as people in police cells or police custody - but not for people in prisons.
Tania Sawicki-Mead is the director of Just Speak, a group dealing with young people in the justice system, and she said she was disappointed.
"The most important thing is that young people who are disadvantaged so early on in life by the very people who were supposed to care for them, to be excluded from the inquiry, that would be a really terrible outcome," she said.
Ms Sawicki-Mead said in the decade to 1999, around 250 young people were given adult sentences and there would be a similar amount in the decade that falls just outside the scope.
"They would have been in those institutions that are excluded, and their experiences in many cases will probably reflect the things that other young people who are included would have experienced," she said.
She said if this inquiry could not address those people, there should be another one.
The Royal Commission said its members were currently reviewing the terms of reference with legal counsel Simon Mount QC.
The chair, Sir Anand Satyanand would then come forward to announce its approach.
However, Male Survivors of Sexual Abuse manager Ken Clearwater said it was not a great start that the lawyers would be the ones to choose who was in and who was out.
"It's going to come down to legal representation, the legal understanding of it and it's going to be pretty complicated all the way through," he said.
He said the $78 million price tag on the Royal Commission could be justified as long as it was thorough, but groups like his who support victims and those working with them also need enough funding to continue their work.
The Royal Commission does expect to make further announcements that clarify the terms, but in the meantime Australian psychologist Michelle Mulvihill is resorting to another kind of psychology to get the commission to think again.
"It will take time, it will cost more money than probably has been allocated, but let's get the job done and let's do it really well," she said.
"New Zealand has a great history of doing things really well around the legal area. Let's continue that and let's do it even better than the Australians did."