Marshall conceded Indian natural rights to reconcile the ruling with American revolutionary ideology

Evidence

But the case did basically pose a poignant issue which concentrated the whole history of the doctrine of discovery. … The contest giving rise to it concerned title to certain frontier lands. … There was, however, the inconvenience, not to say embarrassment, that such a decision ran counter to the impelling ideology of the “American” revolution and its trumpeting of natural rights. … Pre-eminent among these was the right to property. … Appropriately, then, Marshall did recognize that Indian people had “natural rights” in their land, and that this would include the right to transfer ownership (Johnson r. M’Intosh, 1823:563). — David Theo Goldberg, John Solomos, A Companion to Racial and Ethnic Studies, 227