John Howard's gun laws are collapsing, gun control advocates say, as they compile a stocktake on states and territories' compliance with the National Firearms Agreement.

The agreement — which is non-binding, and underpinned by state and territory firearms laws — was negotiated by the then prime minister in 1996 after 35 people died in the Port Arthur massacre.

Preliminary findings from Gun Control Australia's report on the issue indicate a "chain reaction" has been speeding up since 2008. The organisation's chair, Samantha Lee, told the ABC that changes often began with gun lobby wins in NSW.

"As one of the bigger states passes laws to water down their legislation, the other states are following suit … the result being, our national approach to gun control is eroding," Ms Lee said.

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The audit is set to be released next month, and comes as states and territories are moving to implement an update of the agreement signed by the Council of Australian Governments (COAG) last December.

The main outcome of that review was tougher restrictions on lever-action shotguns, after an uproar about the arrival of a new weapon, the Turkish-made Adler A110.

The Adler came in 5- and 7-shot versions, with the latter banned for import by federal justice minister Michael Keenan in 2015.

Shooters were outraged at the ban, believing there was no new technology in the Adler, and no evidence that lever-action shotguns were being used in crime.

Backlash against Adler ban threatens revised national deal

The backlash from shooters has been so strong that some states and territories may baulk at implementing the revised national agreement. So far, only NSW and the ACT have implemented it.

Coalition governments have fractured over the ban, with several federal National Party MPs supporting a disallowance motion by Senator David Leyonhjelm in November, and Liberal MLC Peter Phelps crossing the floor when the enabling legislation reached the NSW Parliament in May.

NSW Police Minister Troy Grant took a public stand against the tougher restrictions until he resigned as deputy premier late last year, at which point NSW fell into line with other states and signed up to the revised agreement.

Mr Grant said at the time that he was standing up for the rights of law-abiding gun owners, and did not believe there was any evidence that lever-action shotguns were more dangerous than other weapons available to recreational shooters.

But Background Briefing can reveal that before his resignation, he received — and then overrode — confidential advice about the contentious laws from his own police force.

The heavily redacted advice, signed off by the NSW Police Firearms Registry and obtained under freedom of information laws by NSW Greens justice spokesperson David Shoebridge, says that improved technology means that lever-action shotguns "are now similar, in terms of their rapidity, to pump-action shotguns".

Pump-action shotguns are highly restricted under the National Firearms Agreement.

Although the document did not make any recommendation, Mr Shoebridge said the clear implication of the expert police opinion was that circulation of lever-action shotguns should be just as restricted.

Queensland MP Katter vows to block new agreement

In Queensland, pro-gun state MP Robbie Katter has vowed to move a disallowance motion against any legislation implementing the revised agreement and giving effect to the Adler ban.

The member for Mount Isa — who shares the balance of power in Queensland — said the ban was political opportunism by the Federal Government.

"If it wasn't so serious," Mr Katter said, "it would be laughable that you're going to cut bloody farmers down from seven shots to five shots when you're shooting pigs, that that's going to make people safe in the cities."

Robbie Katter, pictured here with his friend Colin Muller, has vowed to fight restrictions on licensed gun owners. ( ABC RN: Paddy Manning )

Mr Katter's tactic threatens to further fragment the national gun laws.

Ms Lee from Gun Control Australia said gun politics were especially fraught in Queensland, where firearms laws were weakened in 2012 by the conservative Newman government.

"The gun lobby had the ear of [then premier] Campbell Newman," she said.

"He set up an advisory council up there just stacked with gun lobby advocates, and he said that he was pushing to get rid of red tape, but how we see it is that he's actually really significantly watered down gun laws in Queensland."

We'll see what it means for public safety: Leyonhjelm

Senator Leyonhjelm, a pro-gun Liberal Democrat, said he believed it was likely that Queensland would not follow through with the revised agreement.

He told the ABC he would be "perfectly happy" if Australia went back to the situation before 1996, when the national gun laws were introduced.

"If, as a result of Queensland not signing up to this COAG agreement regarding lever-action shotguns, because of that, the National Firearms Agreement starts to lose relevance, all it will do is take us back to situation that applied 20 years ago when the states did their own things," he said.

"What we will see is some states taking a fairly strong approach and some states taking a less strong approach, and we will see what the result is in terms of public safety.

"My view is we will see no difference between them in public safety because I think in the context of the gun laws in Australia gun control laws and gun violence are independent variables … they are not related."

Joyce criticised for tweet on massacre anniversary

Ms Lee said pressure from an ascendant gun lobby had been having an effect on the National Party in particular.

She pointed to a tweet by then acting prime minister Barnaby Joyce, who wanted the 5-shot Adler to remain available for recreational shooters, on April 28, 2017 — the 21st anniversary of the Port Arthur massacre.

The tweet shows a meeting two days earlier with Robert Nioa, whose company imports the Adler into Australia.

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"It's a very provocative [tweet], and very insensitive to be placed out there in the community on the Port Arthur anniversary," Ms Lee said.

"But it does sum up the re-courting of the gun lobby, particularly by the National Party, and the division within the Coalition between the National Party and the Liberal Party in regards to gun laws here in Australia.

"Barnaby Joyce knows the significance of dates, and that he obviously would have known the significance of this date."

The Deputy Prime Minister was approached for comment but did not respond by deadline.

Changes to laws around security checks, gun clubs

As an example of the steady watering-down of gun laws, Gun Control Australia's audit highlights state moves to abolish the requirement, under the original National Firearms Agreement, to conduct security checks when a firearm licence holder seeks to accumulate additional hunting firearms.

In 2008, the NSW Shooters Fishers and Farmers Party's Firearms Amendment Bill proposed a removal of the 28-day waiting period for subsequent firearms. The bill passed with support of both major parties.

"At the time the Labor Party was needing support to pass its electricity privatisation bill, and the Shooters Party held the balance of power in the NSW Legislative Council," Ms Lee said.

"It was a done deal. The easy passing of this bill sent a strong message to the gun lobby in other states that governments were willing to do deals ... it wasn't long before Queensland, Victoria, South Australia, Western Australia and Tasmania all followed suit."

She said a similar pattern could be seen in the laws that allow members of the public to shoot unlicensed at gun clubs.

"It really does come down to what governments think they can get away with and at the moment they have got away with way too much," she says.

Greens urge 'vigilant approach' to avoid following US

NSW Greens MP David Shoebridge said gun control advocates needed to be aware of gun lobby tactics.

"When it comes to gun laws we either defend them or we let them fall apart like happened in the US," he said.

"The US didn't lose the war on guns and firearms at one moment. It was eaten away by the gun lobby with one law after another law after another law.

"What was billed as a minor reform after minor reform after minor reform and they finally got to where they are now, a society saturated in firearms.

"Those of us in the gun control [movement] in Australia see what happened in the United States, and that's why we take a very vigilant approach to any watering down of our gun laws."

But NSW Shooters, Fishers and Farmers party MP Phil Donato said his party was not pushing for American-style gun laws.

"I don't want to see everyone in the community have access to a firearm," he says.

"There are people in the community that shouldn't have firearms, but let's not let's not further punish the law-abiding people doing the right thing."