In the late 1800s, the American bison had received legal protection in only a few states (e.g., Idaho, New Mexico), but only after they had been exterminated in those states. It wasn't until the early 1900s that serious legal action and attempts to regrow the herds were made. At that point there were only a few thousand remaining in the wild or captivity, so to claim (as the narrator does) that unscrupulous hunters illegally hunted bison is not accurate - immorally perhaps, but not illegally.