The submission can be found here:
Canada appears to be still hiding its submission from the public. The submission has been leaked to various individuals, however, and I have seen a copy. Reading the EU submission gives a pretty good idea of what Canada is arguing.
One of the most unusual of Canada's arguments is that it is simply impermissible under the WTO rules to draw distinctions between aboriginal and non-aboriginal products or economic activity. But aboriginal rights in Canada's own constitution, as interpreted by the Canadian Supreme Court, require differential treatment in certain cases. exempting aboriginal production from general regulatory restrictions, where traditional practices central to aboriginal culture are concerned. Is the Canadian government using the Seal Products case to make the WTO a basis for weakening aboriginal rights?