Hemp and marijuana are both of the same genus and species, they are legally differentiated by their THC content and their intended use.
"Hemp" has been cultivated over time to provide more fiber/biomass than "marijuana", making it a better candidate for textile uses. Because textiles were the intended use the tallest, most fibrous cannabis plants were selected to provide more fiber than oil.
"Marijuana", on the other hand, has been cultivated for maximum THC content mostly for medicinal/recreational use. Because of the desire for resin glands (therefore THC content) the plants that were selected were shorter and bushier for more oil production than fiber. The results of this selective breeding expressed the widest possibilities of genetics of the cannabis plant, leading us to believe them as completely different plants; they are one in the same.
Tennessee state law requires any cannabis derived products must be derived from "hemp", not "marijuana"; it also reclassified "hemp" as having 0.3% THC or less. Determining where any cannabis product was derived from is difficult because the only difference is THC content, not allowing for definitive proof of origin.
You can urge your legislators to have more consumer-friendly cannabis laws here. Enough voices cannot be kept quiet.