Hemp is defined as the plant Cannabis sativa L. and any part of that plant, including the seeds and all derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers, whether growing or not, with a delta-9 tetrahydrocannabinol (THC) concentration on a dry-weight basis of no more than 0.3% (7 U.S.C. § 1639o(1)). Cannabis is marijuana if it has a delta-9 THC concentration greater than 0.3% but is hemp if it contains no more than 0.3% THC. Hemp and its derivatives are typically non-psychoactive when consumed.

Hemp has a long history in North America and was cultivated in the US up to the early part of the 20th century, when domestic production declined. The passage of the Marihuana Tax Act of 1937 was intended to bring marijuana under federal control but inadvertently affected hemp. The Controlled Substances Act of 1970 (CSA), which replaced the Marihuana Tax Act, made all cannabis, including hemp, a Schedule I controlled substance that could not be grown without a permit from the Drug Enforcement Administration (DEA). Federal law gradually eased restrictions beginning with the 2014 Farm Bill, which allowed the cultivation of hemp under state pilot programs. The 2018 Farm Bill effectively legalized the cultivation, processing, distribution, and sale of hemp by removing it from the CSA definition of marijuana. For more information about the 2018 Farm Bill and hemp, see Practice Note, Hemp and the 2018 Farm Bill: Overview.