Cannabis referendum: Is proposed legal limit too high?

Opponents to cannabis legalisation say the amount people could buy each day would make those with heavy addictions worse.

But those who support it say buying up to 14g of dried weed would be just like any other shopping trip, and would not be used all at once.

It is one of the key areas of debate for those weighing up the Cannabis Legalisation and Control Bill ahead of next month's referendum.

The bill that has been put forward is a guide for how legalisation might work, and suggests a daily purchase limit of 14g of dried cannabis or the equivalent of that.

According to research in the United States, that would equal roughly 42 joints.

But if you talk to regular users in New Zealand, they suggest 14g would be more like 20 to 25 joints, if that is the way you consume your weed.

Aaron Ironside, who leads the Say Nope to Dope campaign, said that limit would make it easy for heavy users to keep up their habit.

"We try to help people not develop cannabis addiction, so giving them access to much more than they could hope to use in a day does nothing to help people with problem behaviour," Ironside said.

"The point in Uruguay was that they wanted to make people have to turn up to the shop, not just to do that, but also because then they would be logged as someone who was using regularly and that would help assist that person if their behaviour was getting out of control."

In Uruguay the purchase limit is 40g a month, or 10g per week.

The drug is far more restricted in Uruguay than it would be if legalised here, or compared to other countries with legalised recreational cannabis use.

But does that mean Uruguay is preventing heavy cannabis use that Ironside is concerned about? No.

"I think that's the whole point of why it is we oppose this bill," Ironside said.

"It is the pretence of control, and ultimately trying to control it through these artificial mechanisms does nothing to actually help people with problematic behaviour.

"The answer is in strengthening our health and education approach. That doesn't require you to set up a cannabis shop."

Regular users RNZ has spoken to say it is possible to go through 14g of cannabis in a day, as some opponents to the referendum suggest would happen, but it is highly unlikely.

They say 14g would usually last between two to four weeks, while some less regular users could take six months to get through that much.

Ironside compared the purchase of 14g of cannabis to being able to buy three bottles of vodka in one day.

But under New Zealand law, there is no limit on alcohol sale, and consuming that much vodka in a day would cause serious alcohol poisoning and possibly death.

Consuming 14g of weed in a day would have varying effects, but death is not one of them.

Ross Bell, the head of the Drug Foundation, compared the 14g limit to a weekly supermarket visit.

"You are not necessarily going to consume everything you bought in one go.

"When we do our supermarket shopping we will buy enough household goods for that week," Bell said.

"We're not going to be using all of our toilet paper in one go, so when someone buys 14 grams of cannabis, that actually might last the average user two, three weeks."

Bell said it is important that people who are heavy users and rely on cannabis are given easier access to the drug, along with greater supports promised with the introduction of the bill.

"I think people who have cannabis dependency who are using really heavily need to be provided help.

"We need to, one, provide that treatment, make sure that treatment is available, and two, remove that barrier of fear. Keeping something illegal makes it really scary for someone to admit that they need some help."

Ironside said those supports can be put in place for heavy users without legalising recreational cannabis.