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 0.2% THC and is not advertised as providing a medicinal benefit.
In fact, the U.S. Food and Drug Administration (FDA) approved Epidiolex (a drug made with a purified form of CBD oil) in June 2018 for the treatment of seizures associated with two rare and severe forms of epilepsy in patients 2 years of age and older. These two epilepsy forms are known as Lennox-Gastaut syndrome and Dravet syndrome. Epidiolex is the first FDA-approved drug that contains a purified drug substance derived from marijuana.