But today, police have announced new rules, which immediately come into force.
Would-be purchasers are now required to physically take their purchase order into a police station and present their firearms licence to be checked by a police arms officer.
"Once police are satisfied, the form will then be passed to the dealer by police following verification," a statement released to NZME News Service says.
"This will negate any need for dealers to cross check details - though police will be continuing to audit dealers on a regular basis to make sure the system is working appropriately.
"We will also be working with dealers to ensure they are clear about the process."
The statement added: "Police consider that the firearms regime generally is robust, but we are committed to making improvements where appropriate, and this is an ongoing process."
Heather Du Plessis-Allan would lose against Gun City millionaire, says law expert
Gun City's millionaire owner David Tipple told the Herald last night that he would go ahead with a private prosecution against du Plessis-Allan if a police investigation into the current affairs sting decided against prosecution.
"I'm ready for the battle," he said. "She's going down 100 per cent."
Today, law expert Professor Chris Gallavin, deputy pro vice chancellor at Massey University's College of Humanities and Social Sciences, said it was "likely" that du Plessis-Allan had committed an offence.
"But there is a broader public policy issue here, over whether we want good investigative journalism in New Zealand exposing things that under ordinary circumstances perhaps wouldn't have been brought to either the police or the public's attention," Prof Gallavin said.
"This is one of those cases where discretion should be exercised by police in not prosecuting."
Mr Tipple, however, could bring a private prosecution, Prof Gallavin said. And he believed that it would "have the perversity of a likelihood of being successful, if it was to be brought".
But the former dean of University of Canterbury's law school said that a discharge without conviction would be the "most appropriate" outcome.
The closest New Zealand has come to public interest defence case was the Waihopai spy base trio who admitted damaging a satellite dish shield in 2008, claiming they were defending the public because of the information being gathered was being used for what they though were illegal wars overseas.
Any prosecution likely would be against the reporter, du Plessis-Allan, rather than her employer, MediaWorks.
"They will be pinning it against an individual," Prof Gallavin said.
He was doubtful that a civil prosecution, or defamation case, could be brought by Mr Tipple.
TV3's Story broadcast about the gun purchase came after co-host du Plessis-Allan told Radio Live the .22 rifle had been bought for $300 using a fake name and fake gun licence.
"It wasn't difficult for me to do this. I didn't have to make fake IDs or anything."
It was worrying she was able to buy a gun "under the name of someone who doesn't exist", she said.
University of Canterbury criminologist Greg Newbold doubted that criminals or gangs would've been exploiting the suspected online loophole.
"The real issue is the number of illegal firearms held in unlicensed hands," he said.
"There's a big underworld trade, with a helluva lot of shotguns, .22s [rifles] and pistols in the hands of people who are unlicensed. They circulate in the black market quite frequently.
"Heather [du Plessis-Allan] could've bought an illegal firearm much more easily than going through that process."
MediaWorks journalist Duncan Garner, who interviewed du Plessis-Allen, said the rifle had been bought to test the law and there was a strong "public interest" defence.
A spokeswoman for MediaWorks said: "We believe it is in the public interest that this serious loophole in the gun laws is closed. We support this story and the Story journalists completely."
Inspector Peter Gibson said the investigation was launched after an allegation emerged that false details had been used to fraudulently obtain a firearm via an online dealer.
Possessing a firearm without a licence is a criminal offence and can lead to three months in prison or $1000 fine.
The charge for "obtaining by deception" carries penalties of up to seven years in prison.
"Police take any incident involving the illegal obtaining or possessing of firearms extremely seriously," Mr Gibson said.
A police review of firearms licensing is already underway, and includes an audit of the country's largest online retailer.
The audit had revealed no problems with online sales, police say, but a wider audit of all major online gun dealers is being carried out.
Police are also updating their systems for buying guns online, meaning those doing so would have to go to a police station and show the police arms officer the firearms licence before any online purchase was approved.
If approved, the documentation would then be passed onto the dealer directly by police.
NZ GUN STATS:
• Police believe there are around 1.5 million firearms in New Zealand.
• There are around 230,000 licensed firearms owners.
• Customs figures show that since 2005, on average, 55,000 firearms are imported every year.
