The short answer
Federal law allows hemp and hemp-derived compounds when the product holds no more than 0.3 percent delta-9 THC on a dry weight basis. That number comes from the Agriculture Improvement Act of 2018. Congress removed hemp from the Controlled Substances Act, so hemp is not a Schedule I drug at the federal level. The same law left room for delta-8 THC, delta-10 THC, HHC, THCP and other compounds made from hemp. Federal agencies read parts of the law in different ways. States write their own rules, and about 20 of them have closed that door.
What the 2018 Farm Bill covers
The law defines hemp as Cannabis sativa L. and any part of the plant, including seeds, extracts and derivatives, with delta-9 THC at or below 0.3 percent on a dry weight basis. Hemp must be grown under a USDA-approved state or tribal plan, or under a federal plan in states that have none. A crop that tests above the limit is subject to disposal and, in some cases, a negligent violation finding. The 0.3 percent limit applies to delta-9 THC. It does not list delta-8 THC, HHC or THCP by name.
Delta-8 THC and other intoxicating cannabinoids
Sellers argue that the 0.3 percent delta-9 limit covers delta-8 and similar compounds, because those compounds come from hemp. DEA has stated that delta-8 THC made by synthesis from CBD can fall under the Controlled Substances Act as a controlled substance analog. A 2022 ruling from the Ninth Circuit Court of Appeals treated delta-8 products with 0.3 percent or less delta-9 THC as lawful under federal law. No Supreme Court case has settled the question. The FDA has taken a separate position. The agency says delta-8 THC is not an approved food additive, and it has sent warning letters to companies that sell the compound in food or as a supplement.
State law decides most of it
State rules carry more weight than federal rules for most buyers. About 20 states ban or restrict delta-8 THC by name or under analog drug statutes. Some states cap total THC per package. Some cap milligrams per serving. Some require child-resistant packaging and third-party lab tests. Other states, several with no adult-use marijuana market, allow sales with few limits. A product that is legal in one state can be a controlled substance one state over. Check state attorney general guidance or department of agriculture rules before buying or selling.
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Convenience drives the market
Hemp-derived THC reaches buyers through gas stations, smoke shops, vape stores and online sellers. Those channels operate in states with no dispensaries and in states that have them. A buyer gets a single gummy, a vape pen or a canned drink within a few miles of home, with no medical card and no dispensary queue. The 0.3 percent dry weight rule also allows high doses in a small package. A 5 gram gummy at 0.3 percent delta-9 THC can hold about 15 milligrams of THC. That gap between the letter of the law and the dose on the label sits at the center of the debate. Congress has filed bills to ban intoxicating hemp cannabinoids. None has become law.