The number of Kiwis being found guilty of cannabis-related crimes continues to fall, with only 2129 convicted in the 2018/2019 financial year - down from 6874 a decade ago.
Figures from the Ministry of Justice show the number convicted has fallen every year for the past decade. The number of charges being laid has fallen from 17,116 in 2009/10 to 6132 last year, falling every year but 2016/17.
Massey University senior drug researcher Chris Wilkins says a change in police attitudes is partly responsible.
"This trend has been going on since the late 1990s, but there's been a real reduction in arrests [lately]," he told The AM Show on Thursday.
"The court system was not changing, so they were pretty much giving out the same sentences they always did. The big change was the police were literally arresting a lot fewer cannabis users."
But another driver has been the rise in popularity of harder drugs. A study published on Wednesday found 28 percent of Kiwis have tried methamphetamine, surprising researchers.
"It just illustrates the way meth has come into this country and dominated the drug scene over the last 10 or 15 years," said Dr Wilkins. As a result, police have had to redirect their limited resources.
"Essentially it was a priority thing - meth had started to emerge in that time, and it was pretty clear to them that was what they should be focusing on."
In 2009/10, cannabis was responsible for 78 percent of all drug charges - it's now 45 percent. In that same timeframe, methamphetamine has gone from making up 12 percent of all charges to 47 percent.
A decade ago 2357 people were convicted merely for possessing cannabis - not selling or growing it, just having it. Last year that had fallen to 347.
Dr Wilkins said warning cannabis users rather than charging them is a "sensible approach" from police, at least while it remains illegal. Kiwis will vote later this year on whether to make recreational use legal. Recent polling has seen support for legalisation falling however, despite support from several health academics and researchers.
"It's not looking good for legalisation at the moment, but I think the Government's preparing to - I'm hopeful they are - educate and communicate what they're proposing. I think there's been a real vacuum there," said Dr Wilkins.
New Zealand Drug Foundation executive director Ross Bell says even if police are charging fewer cannabis users, without legalisation control of the potentially lucrative market will remain in the hands of the gangs, and some Kiwis are still having their prospects ruined by convictions.
"The bottom line is that prohibition isn't working. We have some of the highest rates of cannabis use in the world, particularly amongst young New Zealanders. That approach doesn't work - we need a new approach."
If legalised, Dr Wilkins wants cannabis shops run non-commercially.
"That's been the real problem with tobacco and alcohol - so many outlets, low prices."
National Party drug spokesperson Paula Bennett, opposed to legalisation, says the reduction in charges and convictions shows the current police approach is working, and cannabis is no longer taking up too much of their time.
"I think that we've seen an understanding in society that locking people up or convicting people for low-level cannabis use is not a good use of police's time, the court's time or certainly our prisons."
