Why is cannabis illegal in the UK?

The chequered history of cannabis UK law is anything but simple. It weaves together ancient remedies, colonial trade, international treaties, political decisions, and shifting cultural attitudes. Once an essential part of our economy and widely available for therapeutic applications, it eventually became criminalised, restricted, and pushed to the margins of medicine.

In this educational article, we will trace how cannabis moved from everyday use to prohibition, unpack the UK cannabis laws that shaped the current framework, and explore what this means today for both recreational and medical cannabis access.

If you are interested in finding out more about your treatment options, you can try Releaf’s medical cannabis eligibility checker. It is free, takes less than 20 seconds, and provides clear guidance on whether medical cannabis in the UK could be an option for you.

Is cannabis legal in the UK?

Cannabis remains illegal for recreational use under current UK law. Possession without a prescription, supply, and cultivation are all criminal offences. Patients with a valid prescription may legally carry their medication, provided it is in the original packaging with the prescription label clearly attached.

Penalties for recreational use vary. 

Possession can lead to up to five years in prison, supply or production up to 14 years, and both can carry unlimited fines. In practice, enforcement is uneven. Some police forces issue cautions for small amounts intended for personal use, while others pursue prosecution. This unevenness adds to the complexity of understanding cannabis UK law in daily life.

When was cannabis made illegal in the UK?

Cannabis prohibition in the UK was not a single switch being flipped. It was a gradual tightening of drug laws across the early 20th century. By 1928, cannabis had been brought under the Dangerous Drugs Act, and possession became a criminal offence. This moment is often cited as the UK cannabis ban of 1928, a turning point in the history of cannabis prohibition in the UK.

Hemp in the UK before prohibition

Long before cannabis was outlawed, hemp was a cornerstone of the British economy. By the Tudor era, hemp was so essential that it became a royally mandated crop.

In 1533, King Henry VIII ordered that landowners grow hemp to support the navy’s rope and sails. Queen Elizabeth I went further in 1563, expanding the quota and introducing fines for those who failed to comply. Hemp was a strategic resource, fuelling trade and military power, and for centuries it was deeply woven into Britain’s economy and culture.

This history makes the later ban all the more striking: a crop once mandated by law would eventually be criminalised under law.

For a more detailed look into how hemp has shaped the UK, check out The fascinating history of hemp prohibition

The Dangerous Drugs Acts

The first legal step came with the Dangerous Drugs Act of 1920, which tightened Britain’s control over narcotics in line with international treaties. Cannabis was not yet the focus, but the Act created a framework broad enough to include it when the time came.

That moment arrived in 1928, when Britain, under pressure from the League of Nations (the precursor to the United Nations), amended the Act to add cannabis to the list of controlled substances. From then on, possession was a criminal offence, and Britain had aligned itself with the global push for prohibition.

The 1928 cannabis ban

Why cannabis, and why then? 

In the UK, use was relatively limited, mainly through medical tinctures and imported hemp products. Yet lawmakers portrayed it as a potential social threat.

Part of this reflected economic anxieties. Hemp could outcompete cotton as a raw material, making it a rival to industries with political clout. At the same time, stigma around cannabis was being amplified through racist undertones, with policymakers linking the plant to immigrant and marginalised communities.

The result was a ban that was less about proven harm and more about international alignment, economic rivalry, and social prejudice. In 1928, cannabis shifted from medicine and fibre to a substance of suspicion, reshaping its place in the UK for decades to come.

How is cannabis classified under UK law?

The cannabis classification in the UK has always been more about politics than pharmacology. Officially, cannabis sits in Class B under the Misuse of Drugs Act. Unofficially, it has been a pawn in a decades-long tug of war between scientific advice and political optics.

The Misuse of Drugs Act 1971

When the Misuse of Drugs Act arrived in 1971, cannabis was assigned to Class B. That decision instantly set the tone: cannabis was to be treated as a substance of concern, despite evidence that its harms were not on par with many of the other drugs in the same category (such as amphetamines, ketamine, and mephedrone).

From the start, campaigners and advisory bodies questioned the placement. Was this really a science-based policy, or simply a convenient way to show toughness in the face of the counterculture? 

The question has never really gone away.

Reclassifications and reversals

In 2004, the government did what many experts had long suggested: it moved cannabis down to Class C. This was supposed to signal a more proportionate response. Yet the change lasted only five years. By 2009, with headlines warning about “super strength skunk” and political pressure mounting, cannabis was bounced back into Class B.

This back-and-forth says less about the drug itself than it does about the anxieties of the day. Cannabis classification in the UK has shifted not because the plant changed, but because governments did. The result is a label that tells us as much about political mood as it does about medical risk, and for now, that label remains firmly set at Class B.

Why is cannabis still banned today?

If cannabis has medical value and a long cultural history, why is it still illegal in the UK? The short answer is that cannabis restrictions in the UK have less to do with evidence and more to do with politics, stigma, and regulatory caution. 

Even after the 2018 reform that allowed prescriptions, prohibition remains the default.

Current restrictions on UK cannabis use

As we have already mentioned, recreational cannabis is still fully illegal. Even medical patients face limits: flower cannot be smoked but must be used through a dry herb vaporiser, and possession is only lawful when the product is in its original packaging with a prescription label.

Beyond this, the law draws hard lines. 

Cannabis seeds are legal to buy as collectibles, but not to germinate - quite confusing really. Any product that contains more than 1 mg of THC remains illegal, unless prescribed by a GMC registered specialist doctor. THCA, the raw non-intoxicating acid form of THC, is also restricted because it can easily be converted into THC with heat. These technicalities add layers of confusion and highlight how cannabis restrictions in the UK are built to close loopholes rather than to support patient access, even with the changes brought on by the 2018 medical cannabis legalisation.

Political and social barriers

The deeper reason cannabis is still banned has little to do with chemistry and everything to do with culture. Decades of stigma painted cannabis as a drug of delinquency, amplified by media headlines and political rhetoric. Public support has grown in recent years, but it has not yet tipped into a majority strong enough to force change.

For politicians, keeping cannabis illegal is often the safer move. Calls for reform are regularly met with warnings about mental health, youth use, and public order. The result is that the question of why cannabis is still banned today is not always answered from a base of science, but in terms of political will (or rather, the lack of it).

That is not to say that cannabis is without any risks. Concerns about psychosis and youth use remain front and centre in debates around reform, and for good reason. Research has shown that very high-THC cannabis can act as a trigger for psychotic episodes in a small but vulnerable group, particularly those with a family history of psychosis or schizophrenia. 

Our prefrontal cortex does not finish wiring itself until somewhere around our mid-twenties. That patch of brain handles impulse control, decision-making, and the ability to weigh up long-term consequences. For teenagers and young adults, flooding an unfinished system with high-THC cannabis can tilt the odds toward problems later, especially if there is a family history of psychosis or schizophrenia.

These risks are real, but they are also complex, and far from the blanket dangers often portrayed in headlines.

So, is medical cannabis legal in the UK?

Yes. Since 2018, medical cannabis UK law has allowed cannabis-based medicines to be prescribed. 

The headline was historic: prohibition finally cracked. 

But the reality has split into two very different systems.

The 2018 medical reform

In November 2018, cannabis was rescheduled under the Misuse of Drugs Regulations. From that point, specialist doctors on the GMC Specialist Register could legally prescribe it. 

The NHS, however, set the bar almost impossibly high. 

To this day, it will only consider cannabis prescriptions for two rare forms of childhood epilepsy, chemotherapy-induced nausea and vomiting, and muscle stiffness linked to multiple sclerosis. For everyone else, the door remains closed through our national health provider.

Private medical cannabis clinics UK have opened access 

Private clinics have stepped into that gap, and over the past two years this sector has grown rapidly.

At Releaf, our world-class clinical team specialists are now legally prescribing medical cannabis for a far wider range of conditions, including chronic pain, psychiatric conditions, sleep disorders, neurological conditions, women’s health issues, gastroenterological conditions, and cancer support. This has transformed access for tens (potentially hundreds) of thousands of patients who were previously left with no legal route to medical cannabis treatment options.

FAQs about cannabis laws in the UK

When will cannabis be legal in the UK?

The honest answer is that no one knows. Political petitions and parliamentary debates surface every few years, but there is no current plan for full legalisation. Public support has grown, and some parties have hinted at reform, but the timeline remains uncertain. For now, anyone searching “is cannabis legal in the UK?” will find that recreational use is still prohibited.

Why is cannabis illegal in the UK?

The ban on recreational cannabis in the UK was first implemented largely due to international pressure and domestic caution rather than evidence of widespread harm. Over time, stigma, politics, and cultural fears have reinforced the ban. The reality is that the answer to “why is cannabis illegal in the UK?” has more to do with history and politics than with pharmacology, although it is important to also recognise the risks its use can pose when not clinically overseen.

What are the latest cannabis law changes in the UK?

The most significant reform came in 2018, when cannabis was rescheduled to allow medical use. NHS prescriptions remain tightly limited to rare childhood epilepsies, chemotherapy-induced nausea, and multiple sclerosis-related spasticity. Private clinics, however, can now prescribe for a much wider range of conditions. 

These developments are the most meaningful cannabis law changes in the UK to date, though full legalisation has not yet arrived.

What should you do if you want to access medical cannabis treatment?

While recreational cannabis remains illegal, patients in the UK can legally access medical cannabis through a prescription. Specialists working in private clinics are now able to prescribe cannabis-based medicines for a wide range of conditions, giving thousands of patients a safe and regulated route to treatment.

If you think you may be eligible for a cannabis prescription in the UK, the first step is to check. 

Releaf’s medical cannabis eligibility checker is free, quick, and obligation free. It only takes a few seconds and will help you understand whether medical cannabis in the UK could be a treatment option for you.