The board's May 2010 decision said Western Copper's Carmacks project proposed heap leach method for extracting copper from ore is unproven and poses too many risks to Yukon's environment. The heap leach method the company proposed pours sulphuric acid onto thousands of tonnes of copper ore piled on a rubber liner.

Vancouver-based Western Copper appealed the water board's ruling a month later, arguing that the water board exceeded its jurisdiction by denying the Carmacks project a water licence, even though the project has other necessary approvals.

Justice Ron Veale disagreed holding the water board has jurisdiction over the water that Western Copper proposed to use for its heap leach process and therefore it has the right to make a ruling.

"The viability of the heap leach process is not simply a question of commercial viability, it goes to the very fundamental question of whether the mine can leach the copper without creating water toxification issues that cannot be managed," wrote Veale.

"This decision that the water board ... does have jurisdiction over these mining projects is very important. It ensures that when projects get developed that they will include adequate water treatment programs and initiatives, and they will not pollute the Yukon environment," said Lewis Rifkind, the conservation society's mining director.

"The message is very clear, proponents planning to develop projects in our traditional territory must work with us and must be committed to the principle of sustainable development in order to move forward," said Eddie Skookum, Chief of Little Salmon/Carmacks.