New Zealanders have a big decision to make - by 2021 they will decide whether the personal use of cannabis should be legal.
The referendum is one of the Green Party's policy gains this election - albeit in a form palatable to the referendum-enthusiastic NZ First caucus.
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The question of legalisation sounds simple, but it comes with a set of complicated decisions.
Here are 10 things the Government needs to figure out.
1. What's the point?
New Zealanders are going to need a really clear idea of why a referendum is happening.
Ross Bell from the NZ Drug Foundation says the goal of legalising cannabis would be to reduce harm - the aim could be to reduce the number of people smoking, reducing youth uptake, or reducing the frequency with which people smoke.
But one of the biggest harms caused by cannabis right now is the conviction, he says.
"The majority of cannabis smokers don't get locked up. The issue is getting a conviction, of which we dish out to New Zealanders who largely are Māori and young.
"The law saddles people with a conviction that screws them up in terms of employment prospects. That's a punishment that's going to last a lifetime."
On average, seven people a year are jailed for cannabis possession or supply, but the Drug Foundation says 13,000 people have been handed cannabis convictions in the past five years.
In Canada, the law change was pitched as undermining the power of the black market and helping restrict access for underage users.
2. What does legalising cannabis mean?
Whether cannabis should be legalised seems simple, but it comes with a whole lot more questions.
One of the most immediate would be how commercial the market should be. If cannabis can be bought and sold, would it be a state-controlled market or a commercial one?
Would it mean cannabis becomes legal to buy from a store? Would it be legal to grow your own?
One of the benefits of legalising cannabis is the state profiting from tax on the product. The Government would need to work to find the right level of taxation. Too high and the black market would be tempting. Too low and marijuana might be too accessible.
3. Do we want a market like alcohol or like cigarettes?
The risk of commercialisation is a powerful new industry could be created.
There are nearly a dozen different options for legalisation regimes that aren't profit-driven and commercial says Chris Wilkins, leader of the drug research team at Massey University.
"It's really crucial that when we talk about legalisation that people don't think the only option is creating a commercial market like alcohol - a profit-driven market where you have a little bit of regulation."
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Where alcohol is loosely regulated, tobacco is much more tightly regulated, Dr Wilkins says. Placement, packaging and price is all much more heavily regulated for tobacco.
Dr Wilkins says an example of a market that's not commercial would be a Government monopoly where the Government restricts advertising and the money goes back to the Government, or public trusts that return money to the community. Pokies trusts have to return 40 percent of their profits to the community.
"If I was voting in the referendum, I would want to know that detail."
4. How would communities be kept safe?
Communities will be worried about cannabis being sold near schools, churches and cultural institutions, so decisions will need to be made about where the product can be sold - and whether local government has a role in those decisions.
There would need to be an age limit. In Canada it's the same as the drinking age, which is decided state by state.
If it was 18 in New Zealand, that would mean kids in their last year of school could legally smoke it. How would schools deal with that?
The Drug Foundation says the ideal age limit would be 25, but says that's an "unrealistic goal" and it's more practical to keep it the same as the alcohol limit.
Then there's driving - what would the law be around that?
5. How big can the plants be?
If the Government was to make it legal to grow your own cannabis, would it need to limit the number of plants to prevent a black market springing up in urban backyards?
If the Government was to limit plants to say three, what does that then mean?
Would that be three per household or three per person? Would people be allowed three seedlings and three plants that are mature, or three in total?
This is just an example of the kind of detailed decision that will need to be made.
6. How will Māori be affected?
Drug law is different around the world, and ours would need to be adapted to our land, too.
The Drug Foundation says the law should include equity for Māori as a goal.
"If a regulated cannabis market is developed, the economic benefits [should be] felt by Māori communities," says Mr Bell.
But Mr Bell says this is going to be a tricky conversation for Māori, "because there are already mixed views, including within iwi".
If the model was to allow people to cultivate under a Government-issued licence, would iwi be given first dibs?
In regions like Northland, where there's a strong cannabis economy, "you'd shift people who are currently on the black market onto the legal market", Mr Bell says. "It could give people jobs and the tax would flow back as well."
Some iwi leaders told the Drug Foundation they are interested after having seen benefits to First Nations people in Canada and existing Māori interests in the hemp industry.
Others are saying "there's no way in hell".
7. How would you write the law?
Mr Bell suggests the Government appoint a taskforce.
The taskforce would travel the country, so by the time the referendum comes around there's a draft law.
That's similar to what Prime Minister Justin Trudeau did in Canada . His taskforce travelled the country asking questions about regulations, and then the Government turned it into a Bill.
Dr Wilkins agrees that was a good strategy, saying engaging with the public, local communities and stakeholders will be key.
"If you think about the Psychoactive Substances Act, one of the real problems with that is there was no engagement with the public or stakeholders.
"You need to have honest discussions with people, otherwise they are going to be against it."
8. What about workplaces and universities?
The Government will need to consider how cannabis legalisation could impact workplaces and tertiary institutions around the country. What happens if students or workers turn up stoned?
As part of its law change, Canada is currently dealing with the question of cannabis on campus. The universities spoken to by Canadian news publication Macleans plan to treat cannabis as they currently do alcohol.
9. When will the referendum take place?
Labour's confidence and supply arrangement with the Greens promises a referendum at or by the 2020 election.
Labour and the Greens could be keen to have it take place at the same time as the general election, hoping to increase turnout, especially for the youth.
Holding it at the same time as the election would also save taxpayer money - conducting a referendum isn't cheap.
But the risk is either party could be burned if public opinion turns against legalising cannabis - and three years could be a long time to wait if the legislation is all worked out after the referendum.
10. What about mental health?
Dr Wilkins says there's a lot of evidence linking cannabis use and psychosis, especially for people with pre-existing problems.
He says regulation could mitigate the problems of youth access, but the lack of regulation around the alcohol market gives him cause for concern.
"Do you want cannabis sold from supermarkets? You can buy beer for less than $1 a bottle, so what's your expectations around cannabis?"