The high-capacity lever-action Adler shotgun will soon be more difficult to obtain in Australia after state and territory leaders agree to move it into the most restrictive category.

We've dissected what the fuss with this firearm is all about.

1. What is it?

The Adler is a brand of shotgun that uses a lever action to load fresh cartridges into the barrel. Some Adler A110 models can fire more than five cartridges per magazine, which some shooters argue makes the weapon more effective when hunting pests like wild pigs. Others disagree and say shotguns are not even worth using when hunting feral animals. Either way, lever-action shotguns are not as fast or 'rapid-fire' as pump-action shotguns.

2. Why is the Adler controversial?

The Adler has become the subject of fierce debate for a few reasons:

The Adler A110 has a magazine capacity of seven rounds, with another round in the barrel.

The Adler A110 has a magazine capacity of seven rounds, with another round in the barrel. Gun control lobby groups argue that the five-shot Adler can be modified to be able to hold up to 11 cartridges.

Gun control lobby groups argue that the five-shot Adler can be modified to be able to hold up to 11 cartridges. The Adler's lever action has been described as relatively fast-moving, allowing shots to be fired quickly.

The Adler's lever action has been described as relatively fast-moving, allowing shots to be fired quickly. According to Australia's gun laws, the Adler is classified in the least restrictive gun ownership category — but that could soon change after state and territory leaders agreed to reclassify the weapon.

Weapons that hold up to five rounds will be moved to category B, while any weapon with a higher round count will be reclassified as category D.

3. Why has Adler been so easy to get a hold of?

The crux of the debate is around the classification of the Adler.

It currently sits in the least restrictive category A, meaning that it is relatively easy for licensed gun owners to buy. Category A licences are held by any recreational shooter and limit ownership to the least powerful firearms such as low calibre, bolt-action rifles and shotguns that can take only two cartridges.

Pump-action shotguns, which can be rapidly and have a high magazine capacity, are restricted to category C and D, meaning they can only be used by farmers and professional shooters.

Gun control lobbyists have argued that the Adler should be placed in category C or D because of its high capacity.

The reason the Adler is in category A is because it lever action shotguns were not reclassified when former Liberal prime minister John Howard toughened up gun laws through the 1996 National Firearms Agreement. They were not considered worthy of attention because unlike pump-action shotguns, lever action shotguns did not have high profile in crime.

The Adler shotgun was popularised by Robert Nioa, the son-in-law of maverick independent MP Bob Katter. Mr Nioa tried to import thousands of Turkish-made seven shot Adlers but when a temporary ban was implemented they were remanufactured to become five-shot Adlers.

Gun control advocates consider the Adler's availability a significant weakening of Australia's gun control regime, which they argue has put a stop to mass killings and reduced firearm deaths in this country.

For those on the other side of the debate, the gun simply updates century-old technology and they consider its current temporary ban an overreaction.

4. Why is there an import ban on the Adler?

Following the Martin Place siege, the Federal Government announced a review of the National Firearms Agreement, stating that the 1996 agreement "may not accurately reflect the current operation of the legal firearms market".

Part of the review requires the states and territories to reach a consensus on how to reclassify the Adler. But the states could not reach agreement and in response, the Federal Police and Justice Minister Michael Keenan introduced a temporary ban on all imports of lever-action shotguns with a magazine capacity of more than five rounds.

The states and territories have reached an agreement but the ban has not been lifted yet — each state and territory leader now needs to introduce legislation in their own parliament and get it passed.

5. Are Australia's gun laws being watered down?

The Federal Government has been under growing pressure from within its conservative wing to lift the ban on Adler imports and New South Wales crossbench senator David Leyonhjelm has used the issue as a bargaining chip in negotiations.

But as we saw, it's ultimately an issue that will be decided by the states.

Each state and territory government must now pass individual legislation on the reclassification before the import ban can be lifted.

This could be a problem for Queensland's minority Labor Government, where Katter Australia Party crossbenchers are upset over moves to tighten restrictions.