Groups campaigning against a proposal to construct gas storage caverns in Larne Lough have won their latest legal bid.
The Court of Appeal has agreed that the proposal was "cross-cutting in nature" and any marine licence approval should have been referred to the Executive.
It also found a community fund proposal should not have been taken into account.
The proposal was to use water to hollow out seven caverns, each the size of an average skyscraper.
The extremely salty water would then be pumped out to the sea and the resulting space used to store natural gas.
The campaigners argued that the scheme would leave Northern Ireland locked into fossil fuels for decades but there is a legally-binding target of reducing emissions to net zero by 2050.
Lady Justice Keegan said the ministerial decision that the project was not deemed significant or controversial was “irrational”.
Campaigners applauded after she left the court.
Lisa Dobbie from the No Gas Caverns group has been campaigning against the proposal for years.
“I’m delighted with the outcome, the community have worked tirelessly.
“It’s a win for the community, wildlife and the environment," she added.
The decision was also welcomed by Friends of the Earth, whose director James Orr was in court.
He said the court “upheld what we knew all along, that the former minister erred in law by approving the marine licence."
He said it was also "great news for wildlife in the Lough, energy security in terms of exiting fossil fuels and protecting the climate.”
He said the significance that the court placed on major fossil fuel developments being referred to the Executive was important for future decisions.
The court will decide whether to fully quash the granting of the marine licence and the awarding of costs in a hearing on 27 June.
The Department of Agriculture, Environment and Rural Affairs has been asked for a response.