If New Zealand decriminalised cannabis, it won't change very much, according to a leading drug researcher.
In the 20 years to 2014, the number of arrests for cannabis per 100,000 head of population dropped by 70 percent, while the number of people who received warnings rather than criminal charges doubled, according to data from Massey University.
Yesterday at a conference, police union head Chris Cahill said it was high time New Zealand had the conversation about law reform - but cautioned that policing legalised cannabis would be difficult.
Massey University Associate Professor Chris Wilkins told Morning Report the fall in the number of arrests for cannabis use was largely due to the 2010 introduction of pre-charge warnings, which are used instead of prosecuting people.
"Pre-charge warnings are based on the idea that it's not in the public interest to got through a prosecution and bring about a conviction because that would be disproportionate," Prof Wilkins said.
"It's not fair that someone gets caught with a joint at 18 and then that affects their life in terms of being able to get jobs, being able to get finance, being able to travel and all those kind of things."
Increasing methamphetamine use also "changed the game a lot", Prof Wilkins said.
He said it had caused police to reprioritise.
"Quite a few of the people that do get prosecuted [for cannabis] are now just getting fines, that's very much like decriminalisation," Prof Wilkins said.
"So really if you do decriminalise probably you wouldn't get much different outcomes to what you've got."
New Zealanders will have a chance to have their say on whether to legalise recreational use of cannabis in a referendum by, or at, the 2020 general election.
It's part of the confidence and supply agreement between Labour and the Green Party.
However, Dr Wilkins said that before any kind of legal referendum could happen, New Zealanders would need to get clued up on the benefits and risks associated with the drug.
"This referendum - it's really important that pre-referendum there's a really good debate and really good information about the options so we're not voted into a really strict, narrow reform approach that in the end none of us want."