A Turkish court will apply New Zealand law in a hearing to decide custody of a 3-year-old New Zealand boy taken to Turkey as a baby by his mother.

The unusual hearing before the Istanbul Family Court looms as pivotal in the three-year struggle by Auckland publisher Bruce Laybourn to have his son Dylan returned to Auckland.

Mr Laybourn's Turkish lawyer will put before the court a New Zealand parenting order granted in June awarding custody of the boy to the father.

His Turkish-born wife Nil, a New Zealand citizen, took Dylan to Istanbul to visit family in May 2007, when he was 4 months old, but never returned.

The couple had met in Auckland in 2000 and married in 2005.

Efforts to use the Hague Convention on child abductions to have Dylan returned to New Zealand to decide custody failed because of a technical blunder involving Turkish and New Zealand bureaucrats.

Although both countries are signatories to the convention, they had neglected to mutually recognise each other's status.

Mr Laybourn has since spent thousands of dollars to maintain contact with Dylan while battling through the courts to bring him home.

He has had several public stoushes with New Zealand officials and politicians who he considers have not done enough to help him.

In an appeal to the Turkish Supreme Court last year, his Turkish lawyer managed to overturn a divorce ruling and custody order in the mother's favour, issued in his absence by the Istanbul Family Court.

The appeal successfully argued that New Zealand law should have been applied. The rehearing is scheduled for September 30.

If Mr Laybourn wins, he is offering to meet the costs of resettling his wife in Auckland so she can maintain contact with Dylan.

But he has again run into problems getting our officials to provide a formal explanation to the Istanbul court of how New Zealand's custody and divorce statutes are applied.

In Turkey, custody is rarely awarded to the father, whereas New Zealand's Care of Children Act is officially neutral about the suitability of either parent.

Intervention this week by the MP for Auckland Central, Nikki Kaye, prompted action, and Mr Laybourn hopes to send officially sealed documents to Istanbul next week so they can be translated for the hearing.

His New Zealand lawyer, Alex Witten-Hannah, is drafting an "affidavit of applicable law" to accompany the Justice Ministry documents.

A previous Turkish court decision allows Mr Laybourn to spend February and August with his son in Istanbul, although Dylan's lack of English is emerging as a barrier.

"He has reached an age where he wants his dad and can't understand why he can't have me full time in his life."