Buying a handgun in Canada is far more difficult than doing so in the U.S. The new law will make purchasing a firearm in Canada almost impossible. Under the new rules, individuals who don’t already own a handgun won’t be able to buy one unless they qualify for inclusion among a handful of exempt categories such as security guard or elite sport-shooter. While gun reform advocates on both sides of the border have cheered Canada’s further clampdown on gun purchases, some say the new law doesn’t go far enough. Detractors argue the legislation targets the “low-hanging fruit” of legal gun sales while ignoring illegal firearms and their No. 1 source: the U.S. Illegal guns cross the 5,525-mile U.S.-Canada border in myriad ways. Traffickers hide guns in secret compartments in cars and trucks to drive firearms across the border. They smuggle the weapons across less-patrolled areas, like the largely unguarded Montana-Alberta border or the Mohawk reservation of Akwesasne. Gunrunners move illicit items across the St. Lawrence River via speedboat during the summer and snowmobile in the winter. One smuggler tried to pass illegal guns through a public library that straddles both countries.

Canada lives “next door to the world’s largest arsenal of weapons—both military and non-military,” says Robert Gordon, professor and director at the school of criminology at Canada’s Simon Fraser University. “All the bits and pieces for weapons and ammunition are manufactured, and readily available, in the U.S.; there’s no supply shortage or supply chain problems.”

Where do Canada’s guns come from?

Unlike the U.S., Canada’s federal government doesn’t have a national directory that traces the origins of guns on Canadian streets. But various databases and extensive research indicate that many of the guns used to commit crimes in Canada originate in the U.S. Prior to 2012, around three-fourths of firearms used to commit crimes in Canada were trafficked from the U.S., according to the Toronto Police Service. That share dropped to 50% in 2018 as buyers of illicit guns began obtaining firearms from domestic sources. Gun control advocates say that the previous Conservative administration’s relaxation of gun laws contributed to a 50% surge from 2011 to 2015 in Canadian ownership of restricted firearms, a category that refers to guns that aren’t prohibited but are limited to uses like or target practice or as part of a collection.

Still, experts agree that U.S.-to-Canada gun trafficking remains a significant problem for Canada, with rising gang activity, in particular, fueling demand for the weapons.

Canada hasn’t experienced a mass shooting—commonly defined as a single event in which four or more people are killed or injured—since a gunman killed 22 people in Nova Scotia in 2020, the country’s deadliest ever mass shooting. The U.S. has recorded 1,468 mass shootings in the same time frame, according to non-profit organization the Gun Violence Archive. But firearm-related violent crime is on the rise in Canada, increasing 52% to 29 incidents per 100,000 people in 2020 from 19 incidents per 100,000 people in 2013, according to Statistics Canada. (Canada hasn’t released 2021 or 2022 data yet.)

Data from the Toronto police indicate that in 2020, 85% of guns used in crimes in the city—Canada’s largest by population—were trafficked from the U.S., especially from southern states like Florida and Georgia. The Nova Scotia gunman illegally obtained three of his guns from the United States.

The number of guns that moved across the U.S.-Canada border likely surged in the last year. The Canadian Border Services Agency (CBSA) seized over 1,100 firearms at the Canadian border in 2021, more than double the total in 2020 and a 46% jump from 2019. The CBSA declined to comment on the origins of the confiscated firearms and the reason behind the increase in seizures.

Gordon says guns seized by the CBSA are only the “tip of the iceberg” of total weapons trafficked from the U.S. to Canada. According to a Royal Canadian Mounted Police firearms report, Canadian police seized 26,351 guns across the country in 2019, but it’s unclear how many were illegally trafficked from the U.S.

North of the border, individuals must obtain a license, complete a firearms safety course, and undergo an application process that includes criminal record checks, references, and consent from a current or former domestic partner. Canada also mandates a 28-day waiting period, which is often extended, according to Scott Blandford, assistant professor of public safety at Wilfrid Laurier University. Canada also prohibits the sale or purchase of military-style rifles. After the Nova Scotia massacre, Ottawa banned 1,500 types of rifles, including the popular AR-15 firearm. Military-style assault weapons like the AR-15 weapons have “one purpose only: to kill the largest number of people in the shortest amount of time,” Trudeau argued in the days after the attack. “There’s… no place for such weapons in Canada.”

In the U.S., meanwhile, recent changes to gun laws in states like Iowa, South Dakota, and Tennessee have loosened restrictions for individuals to buy guns. Iowans, for instance, now don’t need to obtain permits—which require background checks—to buy a handgun or to carry a handgun in public. Americans can purchase military-style assault weapons like the AR-15 rifle in all 50 states. The U.S. is the world’s leader in firearm ownership, and the only country with more guns than people—120.5 per 100 citizens. Canada ranks twelfth in gun ownership, with 34.7 guns per 100 people.

The difficulty of getting a gun in Canada and the ease of doing so in the U.S. have combined to turn U.S.-to-Canada gun smuggling into a lucrative business. In 2018, after the Toronto Police busted a gun smuggling ring, the agency said U.S. citizens were buying handguns in their country for $300-$500 Canadian dollars (CAD), approximately $235-$390, and flipping them for “anywhere between $2,000-$5,000 [CAD] on the streets of Toronto.”

Because Canada’s restrictions on legal gun purchases are already so tight, gun smuggling from the U.S. to Canada “is the main issue at play” when it comes to combatting gun violence in the country, Gordon says.

The challenges of U.S.-Canada border security

Trudeau’s new legislation will freeze the purchase, sale, import, and transfer of handguns in Canada and enact a new “red flag law” empowering courts to require individuals considered a danger to themselves or others to relinquish their guns to law enforcement. The new law will also increase jail time for gun smuggling and trafficking, from 10 to 14 years.

Studies by governments and advocacy groups suggest that lengthier jail sentences aren’t enough to stop the flow of illegal guns across the border. Moreover, Canadian courts “rarely hand down the maximum [penalty],” says A.J. Somerset, author of Arms: The Culture and Credo of the Gun and a former gunnery instructor with the Canadian army.

Still, many experts insist that gun control laws are needed—and wanted—in Canada. A May survey by the Angus Reid Institute found that 44% of Canadians said the country’s gun laws are not strict enough, compared to 17% who said that gun legislation is too strict. The proposed freeze on handgun sales would limit the number of legally obtained guns circulating in Canada, thereby “not adding to the crimes committed by the smuggled guns,” says Errol Mendes, a professor of law at the University of Ottawa. Gun control isn’t a “complete answer” to solving gun smuggling and violence, but only one piece of the puzzle that needs to work in tandem with better border control and reducing gang activity, says Wayne Mackay, a law professor at Dalhousie University.

Many experts cite the need for additional enforcement along the U.S.-Canada border—which includes two boundary lines, one between Canada from Alaska, and another between Canada from the U.S.’s lower 48 states—but the vastness of the border makes it almost impossible to police.

The U.S.-Canada boundary is the longest international border in the world and is dotted with just 100 checkpoints. It runs through vast stretches of rugged, rural land that’s most unpatrolled except for electronic surveillance like security cameras and occasional helicopter flyovers. The border is “best described as wide open if you know how to navigate it,” Gordon says. “If you’re a hiker, mountain biker or kayaker, you know how easy it is to accidentally, or intentionally, move across the border.”

Roughly 400,000 people cross the two U.S.-Canada borders every day—and that only includes people who do so at designated checkpoints. “The volume of traffic going over the border is huge and we can’t check everyone,” Somerset adds.

Cole Burston—Bloomberg via Getty Images

The Canadian Border Services Agency relies on tools like X-rays and detector dogs to identify “illegal firearms movements at the border,” an agency spokesperson told Fortune. Yet firearms traffickers are using “more sophisticated concealment methods” to get guns across the border, the spokesperson said. Last month, one smuggler attempted to fly a drone cradling a shopping bag full of guns across the Canadian border in the middle of the night.

There are some ways Canada can chip away at the problem of gun smuggling itself. Addressing growing gang activity would reduce demand for illicit firearms, Blandford says. The government can also provide the border services with more tech, tools, and resources to police the flow of guns from the south, he says. Mendes argues that Canada should seek closer cooperation with the U.S. on border and gang intelligence, and that both countries should push gun manufacturers to develop tracking tools that make it harder to transfer firearms from one individual to another. But so long as firearms are readily accessible in Canada’s only land neighbor, guns smuggled from the U.S. are likely to wind up on Canada’s streets. There “needs to be uniform activity and enforcement on both sides of the border,” Gordon says. “Americans have to be in on [the fight against gun smuggling] as well.”