The New Zealand Defence Force is pushing back against a decision to prosecute after a soldier died during a training exercise in 2019.

NZDF did not dispute Lance Corporal Nichols Kahotea's death during a counter-terrorism exercise in Ardmore was a "tragic loss", but is fighting against WorkSafe's ability to file charges against it.

It is understood Kahotea was training to do a "bump landing" which normally requires someone to step off a hovering helicopter onto the adjacent rooftop.

Missing the roof, he fell several stories to the ground below.

The 35-year-old was flown to Auckland City Hospital where he was later pronounced dead.

WorkSafe is prosecuting NZDF for the death under the Health and Safety at Work Act 2015, but NZDF is today seeking a judicial review, saying the act doesn't apply in Kahotea's case.

Their case hinges on a declaration by now retired Chief of Defence Force Lieutenant General Tim Keating which exempts a category of training from the act.

NZDF argued the charges be dissmissed.

WorkSafe said if the declaration was outside of the scope of the act, then it was invalid and the prosecution of NZDF can continue.

Justice Timothy Brewer advised the court this morning that if classified material was discussed, a special clearance would be needed and the hearing would move to a second closed court in the building.

The highly technical hearing came to a close this afternoon with Justice Brewer reserving his decision which will be released at a later date.

A District Court judge earlier ruled the Health and Safety at Work Act 2015 applied to the fatal incident.

NZDF lawyer Sally McKechnie today said the act does not apply to military operational activities.

NZDF had previously argued to have the charges under the act be dismissed by the courts, which was declined by the District Court late last year.

Kahotea's partner sat quietly in the courtroom, acknowledged by McKechnie, who said the soldier's death was a "tragic loss" for his family, regiment and wider NZDF.

Kahotea, of the 1st NZSAS Regiment, was participating in a counter-terrorism training exercise at the New Zealand Special Operations Forces Training centre in Ardmore, South Auckland in May 2019.

His loved ones called him a treasured son, brother, uncle, cousin, partner and father, and described him as a dedicated professional in a public notice after his death.

He joined the army in 2006 as a Royal New Zealand Engineer and climbed the ranks to become an NZSAS operator eight years later.

In a statement posted to social media in 2019, Chief of Army Major General Boswell informed the public of Kahotea's death.

"It is with regret that I must inform you of the passing of Lance Corporal Nicholas Kahotea, a soldier, father, friend and proud New Zealander," he said.

"Nick passed away last night after sustaining injuries in an NZSOF training activity.

"Nick will be remembered as a professional soldier, but more so as a father and friend to many.

"He was an outstanding soldier and a top bloke."

Previous court proceedings had been heard in a closed court because of the material's sensitive nature, with the potential to affect national security.

Today's hearing was heard under strict suppression orders.