The Australian government is seeking legal advice after a 17-year-old Kiwi boy was released from a Victorian adult detention centre instead of being deported.

The teen - who has lived in Australia since age 10 - had been at the Melbourne Immigration Transit Accommodation facility since March awaiting a July deportation hearing, reportedly for non-violent offending.

It is understood he won an Administrative Appeals Tribunal appeal to get his visa back this week.

The New Zealand Ministry of Foreign Affairs on Tuesday confirmed his release and it is believed he is returning to family in Sydney.

The tribunal said it would not be making details of the decision public because it could breach Australian privacy rules. The teen's legal team wouldn't comment due to conditions of the ruling.

A spokesman for Home Affairs Minister Peter Dutton said the "decision has been handed down and the minister is taking legal advice as to options".

New Zealand Acting Prime Minister Winston Peters had accused Australia of breaching UN conventions on children's rights for holding the boy with adults.

"We are joint signatories ... I'm just reminding the Australians: you're a signatory, live up to it," he told reporters.

However, Mr Dutton had shrugged off the criticism, saying the teen would be deported as soon as possible.

More than 600 New Zealanders have had their visas cancelled in Australia since stricter deportation laws came into place in 2014.

Some have spent the bulk of their lives in Australia and have no connection with New Zealand, raising questions about the rights being afforded to Kiwi ex-pats.

In a television program to be aired in Australia on Tuesday night, NZ Justice Minister Andrew Little says the deportation laws lack "humanitarian ideals".

"It seems to me that there is a venal, political strain to all this," he told the ABC Foreign Correspondent program.

"Some Aussies obviously like this, but it's not good for those people. It's certainly not consistent with any humanitarian ideals that I thought both countries once shared."

Mr Dutton told the program every nation - including New Zealand - exerted its own right to deport criminals.

"They're New Zealand citizens, they're not Australian citizens. And it's no breach of human rights," he said.