Cannabis is currently a controlled drug as classified by the Misuse of Drugs Act 1971.
A follow-up to this law, the Misuse of Drugs Regulations Act 2001, placed it under Schedule 1, which is the category for substances with no medicinal value. This schedule currently being considered for review.
Cannabis plants are made up of more than 100 different cannabinoids, which are concentrated to different extents in certain parts of the plant and have different impacts on the body.
The two most well-known cannabinoids are THC and CBD.
THC is the psychoactive cannabinoid - recreational users use it to get "high".
CBD does not have a psychoactive effect.
CBD, unlike almost all other cannabinoids, is not a controlled substance under the Misuse of Drugs Act. For example, industrial hemp (Cannabis Sativa L.) may be grown under licence in the UK. It is a strain of the cannabis plant that contains little or no THC, but does contain CBD.
The Home Office says that CBD oil can contain a maximum THC content of 0.2% and that the THC must not be easily separated from it. CBD oil can be extracted from industrial hemp and, as it is a legal cannabinoid, can be sold in the UK.
CBD oil is thought to have some medicinal properties, including relieving inflammation, pain relief and reducing anxiety, although there have not been conclusive scientific studies on this.
In 2016, the Medicines and Healthcare products Regulatory Agency (MHRA) said that CBD products, if advertised for these medical purposes, needed to be licensed.
Licences for CBD oil as a medicine have not been granted yet but the products can still be sold as long as claims are not made about their medical benefits.