Federal and state laws present marijuana as a dangerous substance requiring coercive control and forbid private citizens from possessing, selling, or growing it. Possession cases brought under these laws depend on a forensic confirmation of taxonomic identity as Cannabis sativa to establish and successfully prosecute a case. Hemp Industries Association v. DEA (2003), a recent federal appeals court ruling, is at odds with this forensic process. American citizens may legally possess and even consume a similar substance—hemp and its derivatives—which can be made into such everyday objects as clothing, rope, and food products. Yet these two plants are both Cannabis sativa and differ only in physical structure and degree of natural tetrahydrocannabinol (THC). Synthetic THC is also a medically prescribed substance, which introduces further confusion into the legal standing of cannabis. Finally, recently, the Ninth Circuit’s second Hemp Industries decision, Hemp II, affirmed the legality of “non-psychoactive” hemp, despite the fact that hemp contains small amounts of THC. This presents obvious difficulties for forensic testing. The differences between marijuana and hemp remain largely social and legal, rather than chemical. These complications present conceptual and practical difficulties for the law, which is structured around neat, mutually exclusive categories. More practically, current forensic tests are incapable of discerning hemp from marijuana because of this legal confusion. This paper investigates the conflicting social, scientific, and legal understandings of marijuana and the potential practical implications of its legal status.