Barrick Gold has submitted a proposal to modify its development consent at the mine to almost double its size and extend its life by 11 years.

Native title applicant Neville Williams started court action against the plan last November.

On Friday, the Land and Environment Court upheld Mr Williams' challenge that the project is not a modification of the mine's existing development consent, but rather a radical transformation.

The court found the proposal is not invalid, but falls within a different approval regime under the Environmental Planning and Assessment Act.

Barrick spokesman Bill Shallvey says the company will appeal against the decision.

He says the company has taken the appropriate avenues to seek approval to modify the gold mine.

"Given the huge investment that we have made out here and the fact that we've also built up an excellent track record since we started, I mean it'd be fair to say that there are not many development projects that have compliance records like Barrick has achieved at Cowal, so we do have some difficulty with the judgment," he said.

"It's our intention to continue to advance this modification.

"Given the State Government's push for stimulus to the local economy and the fact that we're actually an operating project out here looking not only to maintain our current staff levels but to actually increase them, we'd expect that we'll generate some support."

Al Oshlack from the Indigenous Justice Advocacy Network has welcomed the decision.

"In the case of Lake Cowal it's been a fantastic win for the environment and for Aboriginal cultural heritage and for the people of the Murray-Darling Basin in general," he said.

"If Barrick Gold wants to have an expansion as they propose in their modification, they have to go through the proper development approvals that everybody else would have to go through rather than try to sneak it in with a short cut."

The Department of Planning is looking at the court's findings.

A spokesman says the department is getting legal advice on the judgment and its implications.

He says in the meantime it will cease considering the mine application as a modification of the existing development consent.