The Christchurch mosque shooter is representing himself in a fresh legal challenge at the High Court in Auckland tomorrow.
The man is seeking a judicial review and the matter is scheduled for an initial hearing tomorrow morning.
The judicial review will not relate to his murder, attempted murder or terrorism convictions, or his prison sentence.
He was sentenced last August, after he pleaded guilty to all the charges he faced.
He is the first person in New Zealand to be jailed for life without parole - the harshest sentence a New Zealand court can impose.
RNZ understands the judicial review concerns Corrections and the conditions the terrorist is being held in.
He is being held in solitary confinement within Auckland's maximum security prison.
Family members were informed about the court action this afternoon.
Rosemary Omar, whose son Tariq Omar died in the attack, said the news had been hard to take, especially given the timing.
"I think the timing is really pretty bad given the fact it's the first day of Ramadan today, but I'm guessing that's all just the usual cat and mouse games that particular individual likes to play with the community."
She said it might be time for the terrorist to be held with the general population within the prison.
"Maybe the time has come for him to be out of there and in some ways that [being kept in isolation] could be seen as him getting special treatment to keep him safe."