A Ministry of Health document leaked to RNZ shows officials will not even consider extending an amnesty to allow all chronically sick people to use illicit cannabis.
Medicinal cannabis campaigners say the government's dogmatic approach is "ludicrous" and ignores that the current regime is not working.
In late 2018, MPs passed legislation creating a temporary criminal defence so people with life-limiting illnesses could use cannabis while the wider medical regime was being set up.
Ministry officials are required by law to deliver a report to Health Minister Andrew Little by mid-December on whether the amnesty is still needed or should be amended.
But an internal document, obtained by RNZ, shows officials have pre-emptively ruled out expanding the protection to cover people with less serious conditions.
"The review will not consider widening the exemption to medical uses other than [for people in palliative care] or to other drugs controlled by the Act," the paper stated.
Medicinal cannabis advocate Mark Crotty told RNZ the tight parameters were "ludicrous".
"For them to rule out extending it before even listening to patients ... that's awful. At least listen and make a decision from that."
Crotty - who has Crohn's disease - said most patients were still unable to access medicinal cannabis legally due to its prohibitive cost and lack of availability.
"My condition is not going to go away and, so far, the best treatment has been cannabis.
"However, I'm forced into a situation where I have to break the law in order to be healthy because those protections aren't in place [for someone like me]."
Drug Foundation policy and advocacy manager Kali Mercier said the ministry was "jumping the gun" by restricting its review to such a degree.
New Zealand was still years away from having a fully-functioning medicinal cannabis regime, Mercier said.
"There's still very little way for a patient to get hold of legal cannabis. It's very difficult to find a doctor to prescribe it," she said.
"There are very few products available and they're extremely expensive."
Mercier said, as a result, most people had no choice but to use the black market.
"We need to be fair, just, and compassionate. We need to have that exception broadened so that ... it's for anyone who's using cannabis for a severe and debilitating condition."
Green Party drug reform spokesperson Chlöe Swarbrick said the review should be dramatically widened to look at whether the entire system was working.
"That review can be as wide in scope as the minister wants it to be," Swarbrick said.
She said it was "hugely disappointing" the review had instead been seriously limited.
"I don't see a practical approach and I also don't see any form of kindness."
In a statement, a Ministry of Health spokesperson said MPs had mandated the review for a "specific and clear purpose".
"Parliament never intended that the review extend the list of drugs to be exempted for palliative care or include a wider scope of cannabis users," the spokesperson said.
Speaking to RNZ, Little dismissed calls for the review to be widened, saying that would be "a big exercise".
"[The current regime] has already been the subject of a referendum ... and the signal from the electorate was they're not ready for that level of liberalisation.
"We are looking at ways to make sure the regime we've got doesn't criminalise unduly and that is a work in progress."
The ministry's internal document said the review would look into what impact the criminal defence was having and what might happen if it was removed.
The review would canvass the views of police, justice officials, palliative care providers, doctors, nurses, and cannabis users, the document said.
Officials must report back to Little with their findings before 18 December.