Helen Clark has no problem with gangs and others growing cannabis illegally getting licences, should it become legal.
"They've got the experience of growing it," the former Prime Minister told Newshub Nation on Saturday.
"If you're moving to a legal market, why would you exclude the people who have traditionally been growing?"
Clark's foundation earlier this week came out in support of legalising the popular drug, and treating it as a health issue rather than a criminal one. Next year Kiwis will be asked for their views in a referendum.
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"The referendum is not about whether or not people should use it; it's recognising the reality that it's there now," said Clark.
"We could put some rules around it or we continue to have it as a complete free-for-all with no rules at all. So that's why I came down for rules."
She says New Zealand's well-placed to quickly and painlessly convert the black market thanks to existing rules around tobacco, which she helped write.
"You go from Colorado, which is kind of free-market USA, all the way to Uruguay and Latin America, which says you can use cannabis legally if you grow your own, you're in a cannabis club or buy it from a government store.
"Now, we all think, 'We don't have government stores here in New Zealand.' So we have to find somewhere that's in between, and I think we should start with looking at the tobacco level of regulation.
"We do specify an age, we don't allow any advertising or promotion including at the point of sale in the shop, and we can specify content. So that's where I'd start... Look at how we've ended up dealing with tobacco. And it's been a battle, believe me. I've still got the scars on my back from the Smoke-Free Environments Act of 1990 where I stopped the promotion and sponsorship and advertising of tobacco. So let's not even let cannabis go down that route."
Wary of Big Tobacco getting a monopoly on the cannabis market, Clark backs users being able to grow their own.
"I think it's futile to try to prohibit that, but if you're then regulating sale, sale, of course, would have to have a specified content of THC and CBD - the technical components of it. And so I don't think the 'grow-your-owners' should be supplying. I think that needs to come through a legal channel... You can say what age it can be sold at, you can say how it can be sold. You could actually stop it being marketed, which is my preference, you can say what the contents of the cannabis are."
Convictions shouldn't get in the way of criminal growers setting up a legitimate cannabis business, Clark says.
"Those who have cannabis offences should have them wiped, and that includes for growing if there's been no other factor. If there's been violence and they fought the police and brought out a firearm, that's a different matter. But if it's a simple cannabis offence, it should be wiped."
Ministry of Health figures show about one in eight Kiwis use cannabis at least once a year. Most - about 80 percent - have tried it by the time they're 21.