To cost up to $200 million

Examines how the gun buy-back might work.

handguns.

It was similar, but better organised, but there was a difference, as it did not pay gun businesses compensation for loss of trade.

Ardern has signalled those mistakes will not be made here, and gun dealers will be expected to return banned weapons to their suppliers.

Fair prices

O’Leary says ‘‘fair’’ compensation means paying market price.

But the day a ban is announced, the normal market disappears, and the day after a ban comes into effect, there is no market at all, except the black market on which prices could be expected to rise rapidly.

Some of the black market guns in private hands come from burglaries at gunowners’ homes, and restricting supply led to prices for illicit weapons rising in Australia.

O’Leary believes the price the Government should pay for each weapon would have to be its pre-ban price.

Nicole McKee, from gunowner lobby group Council of Licensed Firearms Owners, says compensation in any buy-back should be at today’s market value of the item, not the value after the firearms were banned, because their value would drop.

In a buy-back, owners should also get paid for all the gun accessories they no longer needed, such as magazines, gun-bags and ammunition, McKee says.

It could also include silencers and night-vision scopes, both of which are legal in New Zealand as well, both being popular with hunters.

Calculating compensation

O’Leary says compensation in a fair buy-back should be struck by negotiation between the Government and each owner individually.

‘‘It would mean every firearm would have to sit on a table, and on one side would be the person from the Government and on the other would be the owner.’’

But Wilkinson says a gun buy-back would have to be efficient, and cost-effective, which could rule out such negotiations, requiring another mechanism for setting prices.

Cost of switching weapons

O’Leary says even if people got a fair price for their guns in a buy-back, they would still end up out of pocket.

In Australia many gunowners decided not to buy a new weapon but many switched to hunting or sports-shooting with a firearm that was still legal.

But if Kiwi gun owners get a market price for their older, used gun, many will find it is not enough to buy new weapons.

‘‘I can guarantee they would be considerably out of pocket,’’ O’Leary says.

Total cost

It is hard to know what the taxpayer will have to stump up to buy back semiautomatic weapons.

The Australians didn’t when they embarked on their gun buy-backs.

The best estimate of the total number of firearms owned by New Zealanders is about 1.5 million.

A political consultant who has advised the gun lobby, Simon Lusk, says there are an estimated 19,000 militarystyle semi-automatic weapons in New Zealand.

The cost of buying back banned weapons could be between $100m and $200m.

Money well spent?

The Council of Licensed Firearms Owners does not believe Australians got value for money, and it has urged against tightening gun laws here before a thorough investigation.

The council ‘‘will support our Government and police policy on any legislative changes that are well investigated, have gone through due process and will be effective in reducing the likelihood of a similar terrorist attack occurring in our country again’’, McKee said.

Its website claims the tightening of Australia’s gun laws changed nothing, and that gun crime was falling even before the Port Arthur massacre.

New Zealand has had a similar, slightly higher, level of homicide to Australia, according to the Organisation for Economic Co-operation and Development (OECD) Better Lives index of nations, despite its weaker gun laws that appear to have played a part in why the Australian man charged with the murder of 50 people in Christchurch chose this country, and not his homeland, for the attack.

Researchers have made competing claims for the efficacy of Australian gun controls.

The Harvard Injury Control Research Centre concluded in 2011 that Australia ‘‘seems to have been incredibly successful in terms of lives saved’’.

‘‘While 13 gun massacres (the killing of four or more people at one time) occurred in Australia in the 18 years before the National Firearms Agreement, resulting in more than 100 deaths, in the following 14 years (and up to the present), there were no gun massacres.’’

In 2017, the University of Pennsylvania published more up-to-date findings, which agreed with the Harvard study. Epidemiologic Review in 2016 investigated gun control studies, and found a lot of biased research, paid for by pro and anti-gun lobby groups.

Illegal weapons

There remain massive numbers of guns owned illegally in Australia, though no-one knows how many.

Wilkinson says a buy-back here would not result in criminals handing in their guns. ‘‘It will get a response from law-abiding people and the people who aren’t, won’t do it.’’