National Emergency Management Agency has won its bid to have a WorkSafe charge of breaching its duty to inform tourists and tour operators of the volcanic risk on Whakaari dismissed.

The agency was one of 13 defendants charged by WorkSafe New Zealand with health and safety breaches in the period before the Whakaari/White Island eruption on December 9, 2019.

Forty-seven people were on the island when it erupted, 22 died and many were seriously injured.

Last week in the Whakatane District Court the agency made a legal challenge to have a charge laid by WorkSafe under Section 36 (2) of the Health and Safety at Work Act dismissed.

WorkSafe alleged the agency of failing in its duty to ensure as "reasonably practicable" that the health and safety of other persons, including tour operators and tourists on Whakaari, were not put at risk by the work carried out as part of its business or undertaking.

This would involve taking steps to eliminate or reduce the likelihood of exposing individuals to death or serious injury, including communicating the risk posed to the public by the volcanic activity.

WorkSafe said it was also reasonably practicable for the agency to consult, co-operate and coordinate with the Institute of Geological and Nuclear Sciences Ltd and Whakaari Management Limited regarding the implications of volcanic activity.

The alleged period of offending was between April 4, 2016, and December 10, 2019.

The charge carried a maximum penalty of a $1.5 million fine.

WorkSafe argued the agency had both that duty of care under the Civil Defence Emergency Management Act and Section 36 (2) of the Health and Safety at Work Act.

WorkSafe lawyers submitted its legal interpretation of Section 36 (2) of the Act was in line with Parliament's intention.

The agency's lawyer Victoria Casey QC argued that the Crown agency's functions and responsibilities were much narrower than WorkSafe alleged and NEMA did not have a local operational role.

Casey said WorkSafe's decision to charge the agency was "flawed and misconceived" as it had no operational role at a local level, nor the grounds to issue a warning or alert in the lead-up to the eruption, she said.

"We cannot be held responsible for work that we don't have a statutory duty to do," she argued.

In the Auckland District Court today Judge Evangelos Thomas delivered his decision on the application after hearing two days of evidence last week.

Judge Thomas said in reaching his decision he not only had to interpret the legislation and the main purpose of the Act but also consider Parliament's intentions.

He said the Act makes it plainly clear Parliament's intention was to have a balanced framework to provide for the health and safety of workers and workplaces.

NEMA does not carry out work at Whakaari and it did not send any staff to the island nor did it place any person at harm, he said.

"To accept WorkSafe's interpretation of Section 36 (2) of the Health and Safety at Work Act would clearly go far beyond Parliament's intended statutory purpose of this legislation."

Thomas said expanding the onerous duty beyond what used to be referred to as occupational and health safety obligations would be "significant and controversial".

To do so would create significant additional obligations on businesses, require significant additional regulations, and a much wider monitoring regime," he said.

Judge Thomas said that was clearly not Parliament's intentions and dismissed the charge.