A Canterbury-based website has posted a guide on how to make cannabis oil, a class B drug that carries a maximum penalty of 14 years' prison for making it.
Police have issued a general warning after a New Zealand website posted a guide on how to make cannabis oil and mix it for vaping.
A drug expert says the site is probably "shaky ground".
The website, vapemate.co.nz, has a page headed "Make your own cannabis eliquid NZ".
It contains a step-by-step guide for making cannabis oil from cannabis plant material, then mixing the oil with electronic cigarette liquid.
Tips on using the cannabis vaping liquid are offered too.
"Congratulations, you've now made a highly potent cannabis e-liquid!" the page says. "One drop of juice on an atomiser coil should produce several hits which give you effects of a dab [cannabis concentrate] but much less harsh and much more portable."
"You can use the e-juice in almost any e-cig, and it's highly filtered nature will prevent any clogs …"
"A [particular kind of vaporiser] is great for medicating stealthily on the go."
The process involves evaporating alcohol so venting to outside is recommended - "and use only an electric stove with no open flame - no gas!" the site says.
The Herald received no response to its inquiries to the website, which gives a postal address in Canterbury.
Cannabis oil is a class B drug under the Misuse of Drugs Act.
The maximum penalty is 14 years in prison for making or supplying class B drugs, and three months and/or a $500 fine for possession.
Under the Crimes Act, a person who "incites, counsels, or procures any person to commit the offence" is party to and guilty of the offence.
After being directed to the website by the Herald, the police said anyone providing advice on making a class B drug could be considered party to that offending.
"Any company promoting criminal offending is putting itself at risk and may become subject to police investigation. Businesses that actively provide support, guidance and equipment to commit offences can be charged and may be subject to asset seizure.
"For privacy reasons, police cannot comment on whether any particular business is under investigation."
Drug Foundation executive director Ross Bell said: "Medicinal cannabis patients are wanting this kind of information. Until they can get a prescription for this kind of stuff, the only way to do that is to break the law."
"If there is information on the internet on how to do that safely - it can be quite dangerous making cannabis oils - it's difficult to stop that kind of information being on the internet.
"Is it right for a New Zealand company to be providing information about breaking the law? I think that's tricky.
"I would think, without knowing the law in any detail, they might be on shaky ground."
Bell said, based on anecdotes, people were vaping cannabis in New Zealand although the practice wasn't common. Vaping and edible cannabis from black market supplies were used by some people for medical self-treatment.
Cannabis vaping was popular in jurisdictions where cannabis was legal and he predicted it would become so in New Zealand if this country legalised the drug.
Associate Professor Colin Gavaghan, of the University of Otago law department, said the cannabis oil guide seemed more like "counselling" than "incitement" and he doubted a successful prosecution could be mounted.
"My view is that providing info on its own probably isn't enough for liability under this subsection [of the Crimes Act]. Some intent to encourage is probably also required."
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