Some manufacturers ship CBD products nationally, an illegal action which the FDA did not enforce in 2018, with CBD remaining the subject of an FDA investigational new drug evaluation, and is not considered legal as a dietary supplement or food ingredient as of December 2018. Federal illegality has made it difficult historically to conduct research on CBD. CBD is openly sold in head shops and health food stores in some states where such sales have not been explicitly legalized.
Until 2017, products containing cannabidiol marketed for medical purposes were classed as medicines by the UK regulatory body, the Medicines and Healthcare products Regulatory Agency (MHRA) and could not be marketed without regulatory approval for the medical claims. As of 2018, cannabis oil is legal to possess, buy, and sell in the UK, providing the product does not contain more than 0.3% THC and is not advertised as providing a medicinal benefit.
In September 2018, following its approval by the FDA for rare types of childhood epilepsy, Epidiolex was rescheduled (by the Drug Enforcement Administration) as a Schedule V drug to allow for its prescription use. This allows GW Pharmaceuticals to sell Epidiolex, but it does not apply broadly and all other CBD-containing products remain Schedule I drugs. Epidiolex still requires rescheduling in some states before it can be prescribed in those states.
From 2015 to July 2019, the FDA issued 48 warning letters to 23 American manufacturers of CBD products for false advertising and illegal interstate marketing of CBD as an unapproved drug to treat diseases, such as cancer, osteoarthritis, symptoms of opioid withdrawal, Alzheimer's disease, and pet disorders. The FDA said that the letters were issued to enforce action against companies that were deceiving consumers by marketing illegal products for which there was insufficient evidence of safety and efficacy to treat diseases. In July 2019, the FDA stated: "Selling unapproved products with unsubstantiated therapeutic claims — such as claims that CBD products can treat serious diseases and conditions — can put patients and consumers at risk by leading them to put off important medical care. Additionally, there are many unanswered questions about the science, safety, effectiveness and quality of unapproved products containing CBD."
However, when cannabinoids are taken externally, it’s difficult to distinguish between the clinically desirable effects and the therapeutically undesirable effects of various phytocannabinoids. This is because cannabinoid receptors send a variety of signals that often interconnect to coordinate the body’s functions, so it’s hard to tell them apart.