Shortly after Prime Minister Jacinda Ardern announced the ban, US lawmakers and gun-control advocates bemoaned America's lack of action in comparison to New Zealand.
"This is what real action to stop gun violence looks like," Sen. Bernie Sanders, a 2020 presidential candidate, tweeted Thursday. "We must follow New Zealand's lead, take on the NRA and ban the sale and distribution of assault weapons in the United States."
"Public servants didn't stop at offering thoughts and prayers. They chose to act," former Secretary of State Hillary Clinton added .
Though the US did once have its own assault weapons ban between 1994 and 2004, it expired and Congress never renewed it. Subsequent attempts by Democratic lawmakers to re-enact the ban have been largely ignored by Republicans.
Here are some of the hang-ups American lawmakers continually run into when debating assault weapons bans that go beyond the Second Amendment.
The gun lobby
There's one simple difference between the US and New Zealand that will allow the latter country to enact its assault weapons ban quickly, while the former remains unable to legislate most major gun-control issues.
"They don't have an NRA," Gregory Koger, a University of Miami political science professor, told INSIDER. "There's no organization of gun owners and gun companies that systematically and persistently opposes regulations of guns."
But far more effective than the organization's political donations is its ability to mobilize roughly 5 million members across the country to vote for candidates who oppose gun legislation.
For instance, the NRA assigns letter grades to candidates based on their gun-rights records, compiles extensive voter guides, and even has its own media operation: NRATV.
"There are lots of proposals that are supported by wide majorities of Americans, including gun owners, including Republicans, that cannot get passed because the mot powerful organization in this issue space is opposed to action and is aligned with one of the two major parties," he said.
Though New Zealand does, in fact, have its own "National Rifle Association," it bears no connection to the powerful American gun-advocacy organization, and will not be lobbying against the country's new proposed ban, The New York Times reported Thursday.
The definition of an assault weapon
On the occasions when assault weapons bans do resurface in the public discourse, debates devolve into bickering over the definition of what an "assault weapon" is.
There is no definition of "assault weapon" under US law, and the 1994 ban worked around the issue with a complicated series of restrictions that outlawed specific models and banned certain parts or combinations of parts on semiautomatic weapons.
Details of New Zealand's ban are still unclear, as legislation hasn't yet been introduced. But in her press conference on Thursday, Ardern outlined a sweeping plan to outlaw a variety of weapons that can achieve rapid or near-rapid gunfire or hold large amounts of ammunition.
In addition to banning "military-style semiautomatic weapons," also known as MSSAs, Ardern announced that the country will also ban all assault rifles, high-capacity magazines, and "all parts with the ability to convert semiautomatic or any other type of firearm into a military-style semiautomatic weapon."
She also said parts that "cause a firearm to generate semiautomatic, automatic, or close-to-automatic gunfire" will be outlawed.
"In short, every semiautomatic weapon used in the terrorist attack on Friday will be banned in this country," she said.
Koger said the assault weapons ban that Ardern announced Thursday would be soundly rejected if it were proposed in the US but he said Ardern's idea to ban high-capacity magazines could maybe stand a chance.
"This is a recurring pattern in the tragedies that we see in the United States. It's not the guns themselves it's the fact that they hold so many bullets," he said. "Just banning the magazines themselves would be a measure which politicians could consider, which New Zealand is doing rather swiftly."
The sheer number of guns in the US
Ardern said Thursday that the weapons ban will be accompanied with a nationwide buyback program to compensate gun owners for their newly banned weapons.
The New Zealand government estimates that the program could cost up to $200 million. It's unclear how many weapons will ultimately be bought back, but New Zealand's 5 million residents own a cumulative 1.2 million firearms, according to data from the 2017 Small Arms Survey .
For obvious reasons, a similar program would likely be a massively expensive endeavor and a logistical nightmare for the United States, which has an estimated 393 million guns for the country's 326 million people. A 2016 study found that 3% of Americans owned half of the guns in the US.
Beyond that, Koger said, American gun owners are already suspicious of even the mildest gun-control proposals, and often cite their fear of government overreach. Confiscating massive quantities of Americans' property would likely spark outrage.
"It'd be very difficult to get American gun owners to comply with that program," he said.
