Top health officials agreed in November last year that Managed Isolation and Quarantine (MIQ) was "no longer justified" for most returnees, according to a document the Ministry of Health tried to keep secret.
It took another three and a half months, almost 40,000 MIQ stays and seven voucher lotteries before most incoming travellers could enter freely.
At the time the document was signed off, 80 percent of the country's eligible population had been double-vaccinated and Delta was spreading in the community.
Director of Public Health Dr Caroline McElnay wrote to Director General of Health Dr Ashley Bloomfield seeking his agreement to an updated Public Health Risk Assessment.
She wanted it to reflect that "the risk posed by international arrivals transmitting Covid-19 is no longer higher than the domestic transmission risk of Covid-19".
McElnay asked Bloomfield if he agreed the risk was no higher, and if so: "Managed Isolation for border returnees would no longer be justified on public health grounds as the 'default' for people travelling to New Zealand," the document said.
Bloomfield did agree, and he also agreed to brief Covid-19 Response Minister Chris Hipkins, and start creating a plan for making 'self-isolation' the default requirement for returnees.
The memo noted the government might need to speed up its plan for a phased easing of border restrictions in the first quarter of 2022.
Yet it was not until 2 March, 15 weeks later, before the government lifted MIQ requirement for inbound travellers.
University of Waikato law professor Al Gillespie said the delay raised serious concerns.
"The Public Health Response Act, one of the requirements is that the responses must be proportionate. And the advice that was given was that it was a disproportionate response to continue MIQ. If that's the case, the government has to answer why did they continue down this path."
The implications could be vast, he said.
"You've had people who've had their liberty interrupted. You've had people who've paid thousands of dollars being in MIQ. And you've had thousands of people who haven't been able to access MIQ.
"If the government cannot show why this was justifiable ... then there may be considerations of compensation."
Martin Newell from Grounded Kiwis told Checkpoint the revelation that the director-general and the director of health had signed off on advice to phase out MIQ in November last year confirmed what his group had been saying back then.
"The government ... at the time was not following the science and now we have the evidence that shows that they weren't following the best public health advice that they had supposedly been following all throughout this pandemic.
"The risk to Kiwis coming home to those Kiwis travelling from Auckland to the rest of the country was no greater. And now the question has to be answered, why did they wait so long to reopen the border?"
Neil Protheroe found himself unable to return to New Zealand from France in January, caught amongst the huge demand for MIQ spaces.
He said the ministry's memo added "insult to injury" for thousands of people who were unable to travel.
"It's salt in the wound of those who've been really badly treated and in some cases, traumatised, by the whole thing," he said.
Newall said it would "point to a breach of the New Zealand Bill of Rights Act for those people who wanted to come home in that period."
People who paid for MIQ after November should be entitled to ask for their money back, Newall said.
"But it's more the KIiwis who were stuck overseas, weren't able to say goodbye to a loved one or take care of a loved one.
"If you were sitting in an MIQ lottery in November last year trying to get home and you read this news today ... then you would be pretty devastated if that meant you weren't able to say goodbye to a whānau member."
He doubted the government needed months to transition out of MIQ.
The ministry initially refused to release the November document, even when it was requested under the Official Information Act, "citing free and frank expression of opinions".
However, it was released after a review by the Ombudsman.
Covid-19 Response Minister Chris Hipkins responded with a statement.
"The advice considered by ministers at the time said that while the public health risk at the border has changed, there still needs to be a considered transition from Managed Isolation as the 'default' setting for most people arriving in New Zealand, to a new approach," he said.
"It also said the public health risk of any changes to the managed isolation settings needed to be considered and managed alongside the implementation of the Covid-19 Protection Framework and Reconnecting NZ. The timing of the border reopening allowed us the chance to get our vaccination and booster rates up and that's had a huge impact on our management of the current Omicron outbreak."
Epidemiologist Michael Baker agreed with that last comment.
"New Zealand was able to delay entry of Omicron until late January. That was one to two months behind the rest of the world," he said.
MIQ had likely saved at least 10,000 lives, and it had been a fantastic tool for the first year to 18 months of the pandemic, he said.
Hipkins released another statement saying his office received the memo on 16 November.
"Subsequently, on 23 November, the ministry advised that it had sought further advice from Professor Antony Blakely and Professor Philip Hill who had reviewed the advice and provided their own professional and independent opinion. The initial memo ... was not the final advice on this topic."
But the ministry's November document offered little comfort to people like Protheroe.
"The government should be held to account for that, because they keep telling us that they're making the decisions based on scientific advice. Well that seems to be very selective," he said.
Advice had to be 'reviewed by experts' - ministry
In a statement, the Ministry of Health said the public health risk assessment was at a "specific point in time", before the arrival of Omicron.
The advice had to be "externally reviewed by experts in the relevant fields" before it was "formally considered", and the border rules changed, it said.
"During December and early January 2022 the MIQ system continued to play an important role in managing the arrival of an increasing number of border cases with Omicron, and delaying community transmission of the variant in New Zealand as we increased vaccination levels in the population."
The staged and managed removal of MIQ requirements was delayed by the Omicron outbreak, it said.
"The ministry advised the transition away from managed isolation for most international travellers would need to be managed carefully and safely over a period of time to minimise the impact on the health system, vulnerable communities and increase the support available for people isolating at home."
"The ministry advised that further measures such as pre-departure testing, on arrival isolation and testing, were required to minimise that additional risk of community transmission posed by removing managed isolation requirements for most international travellers."