The Arms (Prohibited Firearms, Magazines and Parts) Amendment Bill is being fast-tracked through Parliament with cross-party support, and is expected to come into force on Friday.
The bill, which was drawn up as a quick response to the Christchurch terror attack, would outlaw military-style semi-automatic (MSSA) weapons and assault rifles, though there would be exemptions for guns commonly used by hunters, and by farmers for pest control.
The exemptions would be semi-automatic .22 rifles (with a magazine which holds no more than 10 rounds), as well as semi-automatic or pump action shotguns with internal magazines (holding no more than five rounds).
After six days considering the bill, the committee bowed to pressure for further exemptions to use otherwise banned firearms for pest-control on farms.
But farmers would not be allowed to do the work themselves. Instead they would have to hire a specialised business, vetted by police.
"We consider that there would be some narrow circumstances where use of a prohibited firearm was absolutely necessary to carry out pest control on private land or non-conservation Crown land for conservation, environmental, or economic reasons," the committee report said.
"Our recommendation would allow a private landowner to engage a wild-animal or animal-pest control business to use such firearms while still removing most semi-automatic firearms from circulation."
The Police Association had argued that bona fide collectors should be allowed to keep banned weapons only if they were made permanently inoperable.
The Green Party supported the police union on this issue, but the committee majority considered this to be an "overly harsh" measure that would have reduced the value of those items.
Instead the committee recommended a vital part of the collector's firearm be removed and stored at a separate address, approved by police.
The committee said banned weapons should also be allowed as heirlooms or mementos if they pass a test for reasonableness. They would also need to have a vital part removed and kept at a separate address.
"We believe that such a test should include criteria such as the type of firearm, the nature of the applicant, and the significance of the event the heirloom or memento is linked to."
The bill's new offence for possession of banned weapons raised concerns that it overturned the legal principle of being innocent until proven guilty, but the committee left it unchanged because it was similar to existing possession offences in the Arms Act.
Under the bill, the owner of any land, building or car where a banned weapon was found would be deemed to be in possession of the firearm unless they could prove otherwise.
However, the committee softened the possession offence as it relates to banned gun parts.
The committee also softened the power of the Government to change the definition of what firearms and gun parts should be illegal, removing its ability to replace the definitions completely, but still allowing Governments to change the definitions through Order in Council.
The National Party objected to this, agreeing with constitutional lawyer Graeme Edgeler that such changes should require a parliamentary majority.
"The constitutional repugnance remains," the National Party said in the committee report.
The committee backed up Cabinet in rejecting a plea from shooting groups to allow an exemption for shooting competitions.
"We consider an exemption unnecessary because the bill would not prevent people from competing in shooting disciplines at the Olympic or Commonwealth Games," the committee report said.
"We believe that providing an exemption for sporting competitors would allow more semi-automatic firearms to remain in circulation than we consider desirable for public safety."
The National Party said in its report that it was sympathetic to competitive shooters, and that this issue could be reconsidered when the Government considers further changes to gun laws later this year.
Gun lobby groups had concerns that the bill was poorly drafted and could criminalise many of the 250,000 firearms licence holders. In response, the committee has clarified the bill to ensure that gun parts including suppressors, silencers, and sights from banned firearms would not be illegal if they were then used on a legal firearm.
Act leader David Seymour, the only MP to oppose the bill at its first reading, accused Police Minister Stuart Nash of blocking police officials from advising the committee.
"We were shocked when officials from the police told the committee they could not provide advice because the minister would not let them," Act said in the report.
Seymour said the advice sought was about how likely the reforms would be in removing MSSAs and assault rifles from society.
"We want to put on record that ministerial interference in select committees is deeply troubling, not only to the making of this law, but to Parliament as an institution."
Nash said through a spokeswoman: "The minister gave no such instruction as described by Mr Seymour.
"Officials were being pressed for information about the buyback scheme. It is standard practice for officials to decline to speak to matters outside the scope of the bill.
"It appears the official has reinforced that point and that has been misunderstood by Mr Seymour."
Seymour also backed up the National Party in criticising the Government's ability to decide what to ban without parliamentary approval.
"It appears to mean that the Executive can ban any type of weapon at any time without parliamentary scrutiny."
The committee received more than 13,000 submissions in the 48-hour period that they could be received; about 60 per cent supported the bill, 26 per cent were opposed to the bill, and 14 per cent expressed another view.
The bill is expected to progress through the next legislative stages on Tuesday and Wednesday, receive the royal assent on Thursday, and be in force by Friday.
An amnesty until September 30 will allow people to hand illegal guns to police without fear of being prosecuted.
