New Zealand has agreed to repatriate Suhayra Aden and her two young children, who crossed from Syria into Turkey in February.
The trio were detained after illegally trying to enter Turkey from the Syrian border, with the Turkish Ministry identifying her as a terrorist belonging to Islamic State.
They have been in immigration detention in Turkey since.
In March, former justice minister Andrew Little said he expected, should Aden and her family be brought to New Zealand, that she would be not be detained, but instead, she would be"free subject to conditions" based on the 2019 Terrorism Suppression (Control Orders) Act.
However, that law also gives authorities the ability to pre-emptively track and monitor certain people, including if they pose a "real risk of engaging in terrorism-related activities".
Aden was a dual New Zealand-Australia citizen and grew up in Australia, but Australia revoked her citizenship.
The action caused tension between New Zealand and Australia, with Ardern accusing Australia of "abdicating" its responsibility.
Under international law, children have a right to a nationality and - if possible - to know and be cared for by their parents.
In a statement, New Zealand Prime Minister Ardern said this meant New Zealand was required to take the family in because of obligations not to leave people stateless, particularly for the two children.
"They are not Turkey's responsibility, and with Australia refusing to accept the family, that makes them our's," she said.
"I made very strong representations to Australia that she should be permitted to return there. Her family moved to Australia when she was six and she grew up there before departing for Syria in 2014, on an Australian passport. Unfortunately, Australia would not reverse the cancellation of citizenship," Ardern said.
"New Zealand has not taken this step lightly. We have taken into account our international responsibilities as well as the details of this particular case, including the fact that children are involved."
Speaking in Northland this afternoon, she said she did not accept the explanations from Australian officials and leadership of why Aden would not be allowed to return there.
"I just don't accept it," she said. "Our view was that Australia did have obligations here," she said.
"Everyone will absolutely know the frustration that we've had over Australia's decision to revoke the citizenship of someone we believe ultimately was Australia's responsibility.
She said agreeing to a managed return was "the right step in this case", but any future cases would be looked at on a case-by-case basis.
"In this case the welfare and best interests of the children has been a primary concern."
Australia had made commitments it would not do so again, she said.
"We have been given an assurance from Australia that we will not have another situation where a ... dual citizen[ship] Australia, New Zealand will not be arbitrarily cancelled in this way again."
Asked whether Australia had breached its obligations under the UN Convention on the Rights of the Child, she said that was a question for Australia.
Police and several other agencies had been involved in planning to bring the family to New Zealand, Ardern said.
She gave "absolute assurances" that all the tools available to ensure the safety of New Zealanders had been used.
"Let me be clear, the choice of not accepting a repatriation could well have led ... Turkey to have the person shipped back to New Zealand without any safety contingency. That would not have been right for us, or for the children involved."
"I can assure people great care is being taken as to how the woman and her young children are returned to New Zealand and how they will be managed in a way that minimises any risk for New Zealanders."
The Prime Minister's Office said details about the family's relocation to New Zealand would not be made public, including security arrangements for legal and operational reasons.
Ardern said services to support reintegration was a concern, as well as security. Any investigation over links to a terrorist group would be a matter for police, she said.