The UK Committee of Advertising Practices (CAP) issued an article summarizing the applicable rules for Cannabidiol containing products. Traders and sellers are advised to well consider the applicable legal framework as they are responsible for the classification and overall compliance of their products.
The recommendation reiterates that psychoactive compound THC is a controlled drug and therefore the applicable rules for drug licensing should be observed for products which contain, be it low levels, of THC. CBD products that are attributed any medical effects are prone to be classified as medicinal products requiring the appropriate licenses from the UK Medicines and Healthcare products Regulatory Agency in order to be marketed.
The use of CBD products as food or food supplements on the other hand is subject to the rules applicable to novel foods. CBD extracts in particular are consider as novel foods and require premarket approval based on a safety assessment. In addition, the indication of any statements for CBD food products needs to observe the applicable rules to nutrition and health claims.
CBD - A potted history and how not to hash up (26 Jun 2020) - link