Deputy Prime Minister Grant Robertson says the government has acted as quickly as it could to bring in changes to terrorism laws that will cover planning a terrorist act.
The government has expressed frustration at the inability of authorities to keep the LynnMall terrorist off the streets after a string of court appearances relating to the possession of Isis material.
Ahamed Aathill Mohamed Samsudeen was shot dead by police after stabbing six people inside Countdown LynnMall. A seventh person was also injured.
The Crown tried - and failed - to charge Samsudeen under the Terrorism Suppression Act because planning to commit a terrorist attack is not an offence under current law.
Robertson said legislation to cover planning a terrorist attack, introduced this year, is well progressed and the select committee was close to completing its deliberations.
"In these areas it is important to get this right," he told Morning Report.
"The consequences of getting it wrong are large, and from the government's perspective we think the policy work has been done, the bill is in and the public have now had their say we now get on with passing that law."
Robertson said his government did the work on the Counter-Terrorism Legislation Bill as quickly as it could.
"We were in the process of trying to speed the select committee consideration up so we could get it back to Parliament."
He said it wasn't possible to say for sure whether the legislation would have stopped the attack.
"What we can say is that the crimes that had already been committed by the person wouldn't necessarily come in under this because they had already been dealt with by the court.
"What we do know is that there has been a consistent call for many years, going well back before this government, for this law to be tightened up around the issue of preparation for an attack that is what this law does."
Robertson said there was work going on with the Immigration Act generally, but he was not signalling major change.
"Refugee status is not granted easily so therefore the act of going through and seeing someone deported will inevitably involve rights of appeal," he said.
Immigration NZ turned down Samsudeen's initial application for refugee status in 2012, and that was appealed to the Immigration and Protection Tribunal which granted the status in 2013.
In February 2019 his refugee status was cancelled on the basis of fraud, and he lodged an appeal with the Immigration and Protection Tribunal, but it had not been heard.
"That is a drawn out process but we do have a rule of law that allows people to appeal," Robertson said.
"At this stage they're being looked into, but I'm not saying there will major change there because we do still need - obeying the rule of law and the rights of natural justice - that appeal process."
Auckland District Law Society Immigration and Refugee Law Committee chair Stewart Dalley told Nine to Noon it may have been possible to deport the terrorist if he had been deemed a national security threat.
Dalley said there was provision under the Immigration Act to deport someone considered a national security threat, or convicted of a particular serious crime, even if recognised as a refugee.
"It requires the Minister of Immigration to certify that the person is a national security threat and then the Governor-General to sign the order."
In a statement yesterday Prime Minister Jacinda Ardern said Crown Law advice to Immigration New Zealand was that the individual was likely to be considered a "protected person" because of the status of the country from which he had travelled, and likely treatment on return. Protected people cannot be deported from New Zealand.
Lawyers question why immigration appeal not heard
Dalley said immigration appeals were normally heard in three to six months, and there were questions over why the Samsudeen's appeal had not been heard more than two years after it was lodged.
He said appeals are able to be heard while a person is in custody, which Samsudeen was until July this year.
Immigration lawyer Alastair McClymont said moves to deport the attacker could well have given him new grounds to claim refugee status.
McClymont told Morning Report if Samsudeen was to be sent back to Sri Lanka, the authorities there would probably have been told he was at risk of causing harm in the community and that would open the possibility for arrest, interrogation, and torture.
"Even if his refugee status was revoked because of the fraudulent documents, the act of deporting him back to Sri Lanka would have made him a refugee or a protected person again."
He said the man would probably have been incarcerated, as Sri Lanka was still investigating the networks involved in the Easter 2019 church bombings. One of the churches was in Batticaloa - the same area Samsudeen originated from.
McClymont said it was unclear why the appeal had to wait for criminal charges to be heard.
"They had no relationship to the revocation of refugee status.
"Immigration New Zealand has said that his refugee status was being revoked because of fraudulent documents - that has no relationship to any criminal offending here in New Zealand."