The judge ruled incorrect interpretation of legal terms around protecting the ocean environment "may well have influenced" the outcome of the seabed mining consent.
It was found the decision-making committee's (DMC) conditions either was or contributed to an "adaptive management approach", which was not permitted in an area governed by the EEZ Act, and labelled a "suck it and see" method by appellants.
Adaptive management is allowing an activity with uncertain effects and continually assessing it - any unanticipated effects must be able to be managed by changing or stopping the activity.
The judge ruled that the interpretation was "inconsistent with the purpose of the Act" in protecting the environment from pollution and with the obligation to favour caution and environmental protection if the information available was inadequate.
The error "may well have" influenced the outcome of the consent application, it was ruled.
The Exclusive Economic Zone and Continental Shelf (Environmental Effects) Act requires a precautionary approach where information about effects is uncertain, but permits adaptive management where that may lead to better information. But - and importantly - it is not permitted for discharge consents (such as e.g. dumping 7000 tons of processed sand an hour on the seabed), and for non-discharge consents, is a lot stricter than just "let it happen with a few routine monitoring conditions which we will ignore". National's rubberstampers on the EPA decision-making committee seem to have ignored this, and they've quite rightly been pulled up on it by the court.
As for what happens now, Trans-Tasman will almost certainly appeal. Pollution and environmental destruction is their business, and this is all or nothing, so they'll throw millions at lawyers in an effort to win the right to pollute and destroy, while whining piteously about "chilling effects" and the need for a law change to let them do whatever they want without any restrictions whatsoever. I can't imagine the current government doing that, but National would. So if we want to protect our oceans, we need to keep the orcs out of power.