The release of a Treasury document on taxing cannabis sparked debate at the highest levels of the department - including when information could be withheld in future.
And while some staff were unhappy with media coverage another manager argued Treasury should be involved in debates about groups "who get criminalised due to policies that don't work".
A flurry of media articles followed the release of the internal document that contained brainstorming notes from 2013 and suggested the Government could earn $150 million from taxing legalised cannabis.
As the story captured headlines, Treasury stressed that the documents were prepared for an internal forum designed to test policy thinking, and the findings weren't official.
An email from a staff member to Treasury's executive leadership team on Tuesday July 19 contained a summary of media coverage, including headlines like, "Pot reform equals dollars and sense, says Treasury".
"Despite us issuing statements (direct to media and via Twitter) clarifying the nature of the paper...media have run with the same story line," Treasury leaders were told.
Two days later Ben McBride, Treasury's manager, health, sent a detailed email to the leadership group in response, in which he made a case for why the cannabis document and resulting debate wasn't a bad thing.
"Releasing that info was consistent with Treasury's org strategy. Outward focused, inclusive, diverse, transparent, open," he wrote.
"The feedback I got was that Treasury looked open to having discussion and debate and [are] not afraid who knows it. It counters the argument that Treasury is old fashioned, conservative and captured by politics."
McBride said that while enough work had not been done to form a considered position on the issue, it was important to tackle such issues, particularly if Treasury was serious about helping the disadvantaged and improving outcomes for Maori.
"[If we] want to move away from siloed agency thinking, which I know we are, then we need to engage in those debates about population cohorts who get criminalised due to policies that don't work. Then we shouldn't shy away from uncomfortable debates like this."
Treasury released the cannabis document in response to an Official Information Act request from Nelson lawyer Sue Grey - who acted for a woman who last Friday successfully brought through Customs an ounce of cannabis prescribed to her in Hawaii.
The OIA is designed to promote access to information held by Government agencies and its guiding principle is that information should be released unless there is good reason for it not to be.
Specified reasons under the law include if the information is "free and frank" advice between officials and ministers.
In his email, McBride told other Treasury staff that there had been no legal reason to decline the release of the cannabis document, and it did not meet the definition of free and frank advice because Treasury had not briefed Minister of Finance Bill English.
In response, Catherine Atkins, deputy secretary, strategy, change and performance, said she could see the value in some forum material being released.
"But other times particularly where we might be debating things that [are] really sensitive I don't understand why we can't use free and frank as grounds to withhold.
"Releasing all forum would limit our ability to debate and discuss policy issues in an open way as I would be more concerned about what was written down."
A senior Treasury lawyer summed up in a final email, saying releasing the cannabis document didn't create a precedent effect, and later that day Treasury secretary Gabriel Makhlouf touched on the cannabis document release in an email to staff.
There had been "confused commentary" in the media, he wrote, but that shouldn't stop Treasury being transparent.
"We should help readers understand the context of what's being released, not forgetting of course the importance of observing the OIA's provisions that protect, for example, 'free and frank' advice or issues under active consideration."
Treasury released the email correspondence (which can be read here) between staff members on its website after a further OIA request.
Drawing on the Treasury cannabis document, the New Zealand Institute of Economic Research (NZIER) yesterday released a report (which can be read here) that concluded that legalisation, combined with heavy taxation, regulation and education would be a better way of reducing social harm from the drug.
Debate about cannabis reform has been stirred by former union leader Helen Kelly and the late Martin Crowe using the drug for medicinal pain relief, and new approaches taken overseas including in Australia.
Last week the NZ Drug Foundation released new polling that showed almost 65 per cent of New Zealanders want personal possession of cannabis decriminalised or made legal.