Cannabis legalisation in some US states is blamed for a surge in smuggling of the drug in Britain, with users clamoring to buy marijuana grown in the state.

Last month, customs officials seized almost half a ton of Class B drugs at Heathrow airport during one 10-day period.

Apparently carrying large quantities of "weed" in their luggage, 13 passengers arriving in Britain from Los Angeles' LAX airport were stopped by customs.

On one commercial flight, a 27-year-old man was accused of having 47kg of cannabis in his suitcases, more than twice the maximum allowed.

The luggage of another female passenger stopped at Heathrow on Jan 13 was allegedly found to contain 40kg of the drug.

Although they are from different parts of the United States, they all flew into the UK on the same route from Los Angeles, the oldest was 48 and the youngest 23.

All three have been charged with attempting to import a Class B drug and have been remanded into custody until a court appearance later this month.

Drugs with extra potency

However, the seizures and arrests have raised questions about why American-grown cannabis is suddenly crossing the Atlantic in such large quantities and if Britain is being affected by California's decision to legalize so-called soft drugs.

Cannabis for recreational use has been legal in the state since 2016, resulting in a multimillion-pound industry.

Additionally, it has enabled producers to create highly potent new strains that are in high demand worldwide thanks to sophisticated agricultural techniques.

Apparently to preserve the freshness of the dried plant, some Californian producers market their drugs in sealed cans.

The popularity of American-grown marijuana among British users has led some dealers to invest in canning machines in order to pass off domestic products as Californian.

One of the main reasons the US drug has found a market in the UK may be its increased potency and higher quality.

'Profits made from US cannabis can be higher in the UK'

"Cannabis is the most widely used drug in Europe, and the UK cannabis market is the single largest in terms of consumers - with over 2.5 million users and a revenue of around £2 billion a year," said Lawrence Gibbons MBE, National Crime Agency drugs threat lead.

It is common for organized crime groups to continue selling high-potency cannabis and exporting to illicit markets even in countries where it has been legalized, such as parts of the United States.

In the UK, organised crime also controls parts of the cannabis market, exploiting young or vulnerable people.

The demand for US-grown cannabis is high in the UK - it is viewed as a higher quality product, which means that organized crime gangs can make more money from it - up to twice as much as domestically grown cannabis.

Wholesale prices plummet

US drug experts also claim that legalizing cannabis in some US states has resulted in a plummeting price of the drug, leading suppliers to look overseas for new lucrative markets.

RAND Drug Policy Research Center co-director Beau Kilmer commented: “The bigger picture is that wholesale cannabis prices are plummeting in California. Before legalisation, cannabis used to sell for $2,000 a pound, but now it sells for less than $400 a pound. Farmers sometimes sell their product for less than $200 a pound.

There's still a legal risk for smuggling 30 or 40 kilos - if it does get seized - but you won't lose as much as you would have five or six years ago."

The potency of the marijuana coming out of California also contributed to its global popularity, according to Prof Kilmer.

In Colorado, over the course of six years, we saw the average THC content go from below 15% to much closer to 20%. I haven't seen rigorous longitudinal data from California, but over the course of six years we saw the average THC content go from below 15% to much closer to 20%.

You'll see strains marketed as having 30% THC. I'm sceptical of some of that, but a lot of it is marketed as having over 25% THC. So that can also be a factor.

Despite legalization here in California, there's still a large illegal market exporting to other parts of the country and abroad."