Hemp and marijuana have separate definitions in U.S. law and are subject to different statutory and regulatory rules, which can cause confusion about the legality of CBD. Marijuana is a Schedule I controlled substance under the Controlled Substances Act and is regulated by the Drug Enforcement Administration (DEA). As a result of recent legislative changes enacted in the 2018 Farm Bill, hemp-derived CBD is not subject to regulation and oversight as a controlled substance at the federal level.

The 2018 Farm Bill included a number of provisions intended to facilitate the commercial cultivation, processing, marketing, and sale of hemp in the United States, expanding on policies enacted in the previous farm bill. It expanded the statutory definition of what constitutes hemp to include 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 THC concentration of not more than 0.3%. The 2018 Farm Bill also amended U.S. laws to remove long-standing federal restrictions on cultivation of hemp. Hemp production is now subject to regulation and oversight as an agricultural commodity by the U.S. Department of Agriculture (USDA).