Where the rights of the Aboriginal peoples of Canada are concerned, history and law are inseparable. Lawyers working on Aboriginal claims ignore history at their peril. But the converse is also true - historians whose work involves the Aboriginal peoples cannot afford to disregard law. Nowhere is this more apparent than in Rupert's Land, out of which the province of Manitoba was at least partially created. Solutions to lingering questions of sovereignty, territorial boundaries, jurisdiction, title to land, and so on, all must be sought in the middle ground where law and history overlap. In this article, we will venture onto this ground in an effort to resolve a long-standing debate over the validity of Aboriginal and British claims to sovereignty in that region.