Under 7 U.S.C. 1639o, the federal hemp definition is the plant Cannabis sativa L. and any part of that plant, including its seeds, derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers, whether growing or not, with a delta-9 THC concentration of not more than 0.3 percent on a dry weight basis.1Office of the Law Revision Counsel. 7 USC 1639o Definitions That definition sits inside the Agricultural Marketing Act of 1946, which is why the Secretary of Agriculture, not the DEA, runs hemp oversight. It is also about to change: Public Law 119-37, enacted November 12, 2025, rewrites the definition to use total THC and takes effect November 12, 2026.
Where the Definition Sits in Federal Law
Before 2018, the Controlled Substances Act treated all cannabis as Schedule I. Low-THC industrial hemp and high-potency marijuana shared the same legal category, with narrow exceptions for sterilized seeds and mature stalks.2U.S. Food and Drug Administration. Hemp Production and the 2018 Farm Bill
The Agriculture Improvement Act of 2018 added the hemp definition at 7 U.S.C. 1639o and made two matching changes to the Controlled Substances Act. The definition of marijuana at 21 U.S.C. 802(16) was amended to state that marijuana “does not include hemp, as defined in section 1639o of title 7.”3Office of the Law Revision Counsel. 21 USC 802 Definitions Schedule I was amended to carve out “tetrahydrocannabinols in hemp” at 21 U.S.C. 812(c).4Office of the Law Revision Counsel. 21 USC 812 Schedules of Controlled Substances Together, these changes pulled compliant hemp out of federal drug law and made it an agricultural commodity.
What 0.3 Percent Actually Means
The single number that separates legal hemp from marijuana is 0.3 percent THC on a dry weight basis. “Dry weight” means the plant material is tested after moisture is removed, so the figure reflects THC in the plant tissue rather than in its water content.
Federal testing rules add a wrinkle that catches producers off guard. Under 7 CFR Part 990, laboratories cannot just measure delta-9 THC sitting in the sample. They must account for THCA, a non-psychoactive acid that converts to delta-9 THC when heated. The regulations define “total THC” as the delta-9 THC concentration plus 0.877 times the THCA concentration.5eCFR. 7 CFR Part 990 Domestic Hemp Production Program A crop with low delta-9 THC but high THCA can still fail once that conversion is applied. Labs must also report a measurement of uncertainty with every result, which provides a statistical range around the reported number.
Testing must be done at DEA-registered laboratories, though USDA has repeatedly delayed enforcement because not enough labs have obtained registration. The current deadline allows non-DEA-registered labs to keep testing hemp through December 31, 2026.6Agricultural Marketing Service. USDA Extends Enforcement Deadline for Hemp to be Tested by DEA-Registered Laboratories
What the Definition Reaches
The statute covers every physical and chemical component of the plant. Stalks, leaves, flowers, and seeds all fall within the definition as long as the THC threshold is met, and the law states these are covered “whether growing or not.” Harvested material, dried biomass, and stored inventory get the same legal treatment as a living plant.1Office of the Law Revision Counsel. 7 USC 1639o Definitions
Bringing seeds inside the definition mattered practically. Before 2018, hemp seeds could be treated as controlled material. Now they move freely in interstate commerce, which allowed a domestic seed supply to develop for farmers.
The definition also explicitly reaches derivatives, extracts, cannabinoids, isomers, acids, salts, and salts of isomers. That language is what supports the market for hemp-derived CBD oils, topicals, and other finished products. Refined extracts and isolated compounds remain legally hemp as long as they come from compliant plant material and stay within the THC limits.
The November 2026 Amendment
On November 12, 2025, Congress enacted Public Law 119-37, which rewrites 7 U.S.C. 1639o. The amended text takes effect 365 days after enactment, so November 12, 2026.1Office of the Law Revision Counsel. 7 USC 1639o Definitions
The core plant definition stays similar: Cannabis sativa L. and any part of the plant, with a THC concentration not exceeding 0.3 percent on a dry weight basis. But the measurement shifts from “delta-9 tetrahydrocannabinol” to “total tetrahydrocannabinols concentration (including tetrahydrocannabinolic acid).” That aligns the statute with how labs already test under the USDA regulations, and it closes a textual gap that let some products qualify as hemp based only on their delta-9 level.
The amended law also explicitly includes “industrial hemp” for fiber, grain, and other non-cannabinoid purposes. It then carves out several categories that no longer qualify as hemp:
- Synthetic cannabinoids, meaning cannabinoids that cannot be naturally produced by Cannabis sativa L., or those that can occur naturally but were synthesized or manufactured outside the plant.
- Intermediate hemp-derived cannabinoid products with more than 0.3 percent combined total THC and similar-effect cannabinoids. Intermediate products sold directly to consumers are excluded regardless of THC level.
- Final hemp-derived cannabinoid products containing more than 0.4 milligrams of combined total THC and similar-effect cannabinoids per container.
- Viable seeds from a cannabis plant exceeding 0.3 percent total THC, even if the seeds themselves contain negligible THC.
The 0.4 milligram per container cap is strikingly low. Many hemp-derived edibles and beverages currently on the market contain several milligrams of THC per serving and will fall outside the hemp definition once this takes effect. Products that no longer qualify as hemp become marijuana or regulated THC under the Controlled Substances Act.
Why the Definition Changed
The 2018 Farm Bill defined hemp based solely on delta-9 THC concentration. That left other psychoactive cannabinoids like delta-8 THC, delta-10 THC, and THC-O in legal limbo. Manufacturers discovered they could chemically convert CBD extracted from legal hemp into delta-8 THC, then sell the resulting products as “hemp-derived” because the delta-9 THC stayed below 0.3 percent.
In 2022, the Ninth Circuit ruled in AK Futures LLC v. Boyd Street Distro that delta-8 THC products containing less than 0.3 percent delta-9 THC fit “comfortably within the statutory definition of hemp.”7U.S. Court of Appeals for the Ninth Circuit. AK Futures LLC v Boyd Street Distro That ruling confirmed what the industry already suspected: the 2018 wording, focused on delta-9 alone, left an opening for intoxicating products. The DEA separately concluded that THC-O, which does not occur naturally in cannabis and can only be produced synthetically, is a controlled substance regardless of its source material.
The November 2026 amendment answers both problems. Switching to a total THC measurement pulls THCA-heavy products inside the threshold calculation, and the exclusion for synthetically produced cannabinoids removes products like THC-O and lab-converted delta-8 from the hemp category entirely.
Legal Hemp Is Not the Same as a Legal Product
One boundary worth stating plainly: the 7 U.S.C. 1639o definition governs the plant and its raw derivatives as an agricultural commodity. It does not authorize any particular consumer product. The Food and Drug Administration still regulates what goes into food, beverages, and dietary supplements, and the FDA has concluded that adding CBD or THC to food is prohibited under the Federal Food, Drug, and Cosmetic Act. CBD is also excluded from the definition of a dietary supplement because it is an active ingredient in an FDA-approved drug, Epidiolex.8U.S. Food and Drug Administration. FDA Regulation of Cannabis and Cannabis-Derived Products Including Cannabidiol CBD
The FDA has authority to create a regulatory pathway for CBD in food and supplements through rulemaking but has not done so. Growing hemp is federally legal. Extracting CBD from it is federally legal. Selling that CBD as a food ingredient or supplement sits in a gray area where the FDA retains enforcement discretion. The hemp definition tells you what the plant is. It does not tell you what you can put in a bottle and sell.