An outcome in the First Nation's favour — coupled with the top court's recent landmark decision to grant land title to the Tsilhqot'in people of British Columbia — could have major consequences on the Conservative government's resource agenda.
Either way, the decision will further clarify the roles of the federal and provincial governments when it comes to resource development on treaty land.
"There's another issue in aboriginal law that has been out there for many years, which has caused a lot of controversy and has made things very complicated, namely: what are the respective roles of the federal government and the provincial governments?" said Robert Janes, lawyer for Grassy Narrows.
"Aboriginal people simply take the very strong view that the federal government has a special role and should be involved in this. That's the issue that's going to be addressed in the Keewatin case.
"In the Tsilhqot'in case, the Supreme Court of Canada gave some hints that it sees the federal government as having a lesser role and the provinces are at the forefront. But we'll have a better picture on Friday."
The Grassy Narrows First Nation appealed after Ontario's highest court ruled in March 2013 that the province has the right to "take up" treaty land for forestry and mining.
Only Ottawa, they argued, could "take up" the land because the treaty promises were made between the Crown and First Nations.
The northwestern Ontario First Nation has spent more than a decade in court fighting the province's decision to issue a licence for clearcut operations in parts of the Keewatin portion of Treaty 3 territory.
Chief Simon Fobister has said Ontario continues to plan for clearcut logging throughout Grassy Narrows territory and is seeking input on a new 10-year forest management plan that includes dozens of large clearcuts.
The First Nation says scientific studies indicate that clearcut logging in boreal watersheds raises mercury levels in fish above the Health Canada limit for safe human consumption.
It says recent clearcut logging in Grassy Narrows territory has exacerbated the impact of mercury poisoning that began when a paper mill upstream in Dryden, Ont., dumped mercury between 1962 and 1970.
The Ontario case differs from the one involving the Tsilhqot'in people of British Columbia in that it involves treaty rights. Unlike other provinces, the Crown has not signed treaties with most First Nations in B.C.
The Supreme Court's unanimous decision on the Tsilhqot'in case recognized, for the first time in Canada, aboriginal title to a specific tract of land and set a historic precedent affecting resource rights.
The Tsilhqot'in case essentially made it easier for First Nations to establish title over lands that were regularly used for hunting, fishing and other activities prior to contact with Europeans.
The decision places a greater burden on governments to justify economic development on aboriginal land. Title, however, is not absolute. Economic development can still go ahead on titled land without consent in cases where development is pressing, substantial and meets the Crown's fiduciary duty, the high court ruled.
The Ontario case, however, deals with treaty rights and not aboriginal title.
"There's no doubt that in the situation where treaties are involved, the courts have generally taken the view that the lands are more easily opened for development," Janes said.
"There's no doubt that that will help the province advance a resource agenda. But what we've seen in Alberta and northeastern B.C. is that even in those lands, the courts have not said that it's a free-for-all.
"I think what we're seeing is a situation where governments have a slightly easier job, but it's not an open door."
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