Legalising marijuana for personal use is not a silver bullet and won’t see the end of gangs or cannabis-related crime, nor free up police resources to tackle other crime, the Police Association has heard.

The warning comes from police intelligence practitioner and cannabis researcher Carrie Drake, who was one of several speakers at the second day of the association’s annual conference in Wellington today.

The conference theme is about policing cannabis if it were made legal for personal use in New Zealand. A referendum on legalisation by or at the 2020 general election is part of the confidence and supply agreement between Labour and the Greens.

Drake interviewed frontline officers in jurisdictions where cannabis was legal or decriminalised, including US states and the Netherlands, as part of research while at Massey University.

She found that legalising cannabis is often viewed as a panacea, but cannabis-related social harm existed regardless of the drug’s legal status, gangs continued to cause social havoc, and police continued to be called to cannabis-related incidents.

Drake said a US officer told her: “We just have not seen all the wonderful promises that were made to us.”

When association president Chris Cahill asked members for a show of hands from those who expected legalisation to allow resources to be deployed elsewhere, no one raised a hand.

Officers in some US states also told Drake that there seemed to be an increase in drug-affected driving, but testing for impairment was unenforceable.

The difficulty of testing for impairment – not just for drivers, but also workers, including on-duty police officers – has been a major topic of debate in the conference.