The 2018 law change generated headlines suggesting cannabis had been legalised. It had not, and the confusion has persisted ever since because the actual change was narrow, technical and easy to misreport.
Understanding what happened requires separating two systems that operate side by side and are frequently conflated.
The Misuse of Drugs Act 1971 is the legislation that makes drugs illegal. It categorises controlled substances into Classes A, B and C according to how harmful they are considered to be, and sets the penalties attached to each.
Running alongside it, the Misuse of Drugs Regulations 2001 set out the exceptions permitting lawful possession and use of certain controlled drugs for medical, dental and veterinary purposes. The regulations sort substances into five schedules according to medical usefulness and potential for harm, with Schedule 1 reserved for drugs considered to have no legitimate current medical use.
The House of Commons Library briefing on the medical use of cannabis sets the position out plainly: cannabis remains controlled as a Class B drug under the 1971 Act, and it is illegal to possess, produce, supply, import or export it in the UK.
What changed in November 2018 was the regulations, not the Act.
Cannabis-based products for medicinal use moved from Schedule 1 to Schedule 2 of the 2001 Regulations. That single reclassification made it lawful for specialist doctors to prescribe them.
Everything else stayed where it was. Herbal cannabis not intended for medicinal use remained in Schedule 1. The Class B classification under the 1971 Act was untouched. Possession without a prescription remained an offence.
So the accurate summary is that a medical exception was widened, not that a prohibition was lifted. That is a considerably duller headline, which is presumably why it was not the one that ran.
The change did not emerge from a policy review. It followed sustained public pressure in individual cases, most prominently those of children with severe treatment-resistant epilepsy whose families were unable to access products lawfully in the UK while obtaining them abroad.
Those cases created a political situation in which the existing position became untenable, and the government responded with a targeted regulatory amendment rather than a broader reform.
That origin explains the shape of what followed. A change driven by a small number of severe paediatric cases produced a framework built around specialist prescribing and clinical exceptionality, not around general access.
Anyone wanting the fuller account of why is cannabis illegal in Britain will find the history runs back well before 1971, through international treaty obligations that continue to constrain what any UK government can do unilaterally.
A detail that causes endless confusion: two cannabis-based medicines hold a UK marketing authorisation, meaning they have been through the full licensing process. Sativex, a THC and CBD spray, and Epidyolex, a highly purified cannabidiol.
Everything else prescribed in this space is unlicensed, meaning it has not been assessed by the medicines regulator for safety, quality and efficacy. Prescribers may use unlicensed medicines where a licensed one does not meet a patient’s clinical need, which is the legal basis on which most UK prescribing in this area happens.
