Two sisters, Karen Beaumont and Anne-Marie Forsyth, went to court seeking to have the man's name suppression overturned.
He was convicted 20 years ago of sex crimes against them in the 1970s, but they want his name made public.
The judge ruled that naming the man now would be disproportionate but Ms Forsyth said that's only a roadblock.
"It doesn't stop here and we will be back," she said.
"They're saying it will be unfair for him to have to face the public scrutiny now, but in my eyes he has really avoided that public scrutiny for 20 years, so he has really only had half of a sentence until this stage anyway."
Garth McVicar from the Sensible Sentencing Trust told Morning Report this decision would make it harder for other women to come forward in the future.
He said New Zealand's legislation effectively sanctioned the man's behaviour.
"They've got to deal with the offending, it's traumatic, it's incredibly hard on them to have the courage to come forward, and no wonder, and this decision will make it even harder.
"Why would you put your faith in the justice system when you get dealt a blow like this?"
The two sisters are considering what to do next, now that the court has ruled against making his name public.
In the judgement released yesterday, the High Court in Christchurch said naming the man, who was convicted of the abuse in 1995, would amount to re-punishing him.
Ms Beaumont and Ms Forsyth successfully argued last year to have the automatic suppression of their own names lifted.
Earlier this year, they asked the court to quash the man's name suppression too, arguing it was granted to protect their identities, not his.
But Justice Mander said the man had been rehabilitated and had built a new life.
The sisters' lawyer, Nikki Pender, said they were considering their next steps.