Some 47 people were on White Island -- also known in Maori language as Whakaari -- in December 2019 when a deadly column of burning ash and steam blasted from a volcanic vent.

The fatal eruption also left 25 people with horrific burns.

Whakaari Management Limited -- which granted permits to visit the island -- was found guilty of breaching its safety obligations and ordered to pay US$2.7 million in reparations.

High Court Justice Simon Moore on Friday quashed that conviction, finding the company was not responsible for the safety of the volcano's visitors.

Instead, Moore said commercial operators ferrying tourists out to the island were responsible for carrying out their own checks.

"The 47 people who were on Whakaari at the time it erupted should never have been there," Moore said in written findings.

"It is impossible not to be deeply moved and affected by the sheer scale and nature of the human loss in this case."

The eruption off the coast of the country's North Island prompted a massive medical operation that saw victims treated in burns units across New Zealand and Australia.

Since then no boat or aircraft tours have been allowed to land on the island.