The Prosperity mine has twice been rejected by the federal government, but that hasn't stopped a Vancouver company from going to court to get the project back on track.

Taseko Mines Ltd. has launched a constitutional challenge against the Canadian Environmental Assessment Act.

This came after it was refused permission in 2010 and 2014 to proceed with the open-pit copper-gold mine 125 kilometres southwest of Williams Lake.

The company estimates there are 2.3 million ounces of gold and 1.2 billion pounds of copper in the deposit.

The Tsilhquot'in national government will be in Federal Court this morning in Vancouver to oppose Taskeko's bid to overturn the federal rulings.

In a news release, the indigenous government has claimed that the company is arguing that the law "goes too far in protecting the rights of aboriginal peoples".

"In essence, the company is attempting to further reduce the protection of our already gutted federal environmental laws, particularly as they apply to aboriginal people," the Tsilhquot'in stated.

Last year, the company announced that the B.C. Environmental Assessment Office "is proceeding with Taseko's request to amend the environmental assessment certificate for its New Prosperity Gold/Copper Project in central British Columbia".

This has upset the Tsilquot'in national government. It won a Supreme Court of Canada case in 2014 establishing its aboriginal title over 1,750 square kilometres in central B.C.

The proposed mine is just outside this territory.

"Our people have fought long and hard to protect our land and waters," Chief Roger Williams, vice chair of the Tsilquot'in national government, said in the news release. "We will continue to fulfill this sacred responsibility. We draw on our 1989 Nemiah Aboriginal Preserve Declaration and our 1990 Xeni Gwet’in trap line court case that evolved into our landmark Supreme Court title declaration. After two federal rejections this company still tries to bulldoze ahead and cause destruction in our territory. For the past decade we have opposed TML in the strongest terms and it is time they finally understand our position—simply stated, we do not consent.” 

After the federal government rejected the first mine application, Premier Christy Clark called it a "dumb decision".

At the centre of the dispute is the future of Fish Lake, which was going to be turned into a reservoir for toxic waste as part of the first application.

It received approval from the B.C. Environmental Office before being vetoed by the feds.

The company maintained that its second application spared the lake, which is home to thousands of trout.

However in 2014, then Conservative environment minister Leona Aglukkaq declared that the mining project was still "likely to cause significant adverse environmental effects".