This latest legal challenge follows widespread controversy when Bill C-38 was rammed through Parliament in spring 2012. It re-wrote the federal environmental assessment law, weakened protection for fish and species at risk and gave the public less say in major industrial projects like new tar sands pipelines.

Then Bill C-45 landed in winter 2012. It includes new legislation regarding the leasing of reserve lands, First Nations education, on-reserve voting rights, the abolishment of the Navigable Waters Protection Act, and other measure to further weaken environmental protection.

"(Canadians) should be with us in support and send a message to Stephen Harper and his government that what they're doing is wrong. They can't ram bills down our throats and expect us to roll over and accept it because this is going to affect our future, affect the future of Canada," said Mikisew Chief Steve Courtoreille.

"We believe that all Canadians care, just as we do, about protecting our environment and respecting First Nations treaty rights... At the end of the day, we will not sacrifice our treaty rights and the environment for the almighty dollar. There has to be balance," said Chief Clifford Stanley of Frog Lake First Nation.

Robert Janes, counsel for the two First Nations, says the government should have consulted with First Nations as soon as work began on the legislation. Janes expects that First Nations across the country will apply for intervener status.