A First Nation in British Columbia's northwest is taking the provincial government to court over plans to redevelop an open-pit molybdenum mine on lands where it says its members have fishing and hunting rights.

In a petition launched in B.C. Supreme Court this week, the Nisga'a allege, in part, that the provincial government failed to consult the First Nation on environmental issues before issuing an environmental certificate to Vancouver-based Avanti Mining Inc.

The First Nations' leaders accuse the government of breaching the Nisga'a Final Agreement.

But the Ministry of Environment said in a statement issued Friday evening that the provincial government takes the treaty very seriously and consultation was a central aspect of the environmental assessment.

"We continue to work with the Nisga'a Nation, in good faith, on the interpretation of the environmental assessment chapter of the Nisga'a Final Agreement," said the ministry. "The province is of the view that negotiation is preferred over litigation."

The company said in a statement it will oppose the petition, and called the Nisga'a action "disappointing."

"We are confident that the province's EA process is robust and that all environmental and human-health issues have been thoroughly addressed -- years of assessment and thousands of pages tell us so," said Craig Nelsen, the company's president and CEO.

The project would see the historic Kitsault Mine redeveloped about 30 kilometres from four Nisga'a villages and about 140 kilometres north of Prince Rupert, B.C.

The provincial government issued the company an Environmental Assessment Certificate on March 18, 2013, and Avanti Mining Inc. said it is awaiting the results of a federal environmental-assessment.

The Nisga'a state in the court petition that the project will be located in the Nass Area and the Nass Wildlife Area where citizens have treaty rights to hunt wildlife and fish for salmon and steelhead.

"The project now proposed by Avanti at the Kitsault Mine site will include ... an open pit, ore processing plan, low grade ore stockpile, waste rock management facilities, explosives manufacturing facility and a sewage and waste-water management facility," the petition states.

"The estimated ore extraction rate for the project is between 40,000 - 50,000 tonnes per day, over approximately a 15-year operation period."

The petition states the project is expected to produce about 16-million tonnes of tailings annually and will include "elevated levels of arsenic, molybdenum, cadmium, lead and sulphur."

The First Nation alleges the project triggers treaty obligations, and the province is obligated to give the Nisga'a timely notice and all available relevant information on a project with potential adverse environmental effects.

The Nisga'a also state that under the treaty they must be consulted and given the opportunity to participate in any environmental assessment under provincial and federal laws.

The Nisga'a want, in part, the B.C. Supreme Court to suspend the environmental certificate until a dispute-resolution process established by the treaty is resolved, quash and set aside the decision and declare the province has breached its treaty obligations.

Meantime, the company said it is confident all legal and treaty requirements have been addressed.

"While legally exempt from the BC Environmental Assessment process due to its pre-existing mine permit, Avanti voluntarily opted in because of the strong track record of EAO addressing aboriginal and treaty rights," said Nelsen.

He said no decision of B.C.'s Environmental Assessment Office has ever been overturned by the courts.