The New York Times

MEXICO CITY — In 2008, the U.S. gun maker Colt, based in Hartford, Conn., produced a special edition .38 Super pistol that was engraved by a partner company with an image of the Mexican revolutionary Emiliano Zapata. In 2017, an assassin used the weapon to shoot dead a prolific Mexican investigative journalist, Miroslava Breach, as she drove her son to school in the city of Chihuahua. It was a cruel irony: An American gun embellished with an image of a Mexican freedom fighter was used to silence Mexico’s freedom of speech.

Last August, Juan Carlos Moreno, a cartel enforcer, was sentenced to 50 years for his participation in the murder of Ms. Breach, and Hugo Amed Shultz, a former mayor from Chihuahua State, was later arrested over his suspected involvement in the killing. Mexico’s gun laws are so strict that in the entire country there is only one store, controlled by the Army, where citizens can legally purchase a gun. Yet a steady flow of guns smuggled south over the Rio Grande find their way into the hands of assassins. From 2007 to 2019, more than 164,000 firearms were seized from criminals here and were traced to gun shops and factories in the United States.

This is just the tip of the iceberg. Mexico’s Foreign Ministry estimates that more than 2.5 million guns have flooded over America’s southern border in the last decade. In that time, Mexico has been gripped by violence that terrorizes communities and stifles the nation’s growth. Even the pandemic did little to curb the nation’s murder rate, with more than 34,000 homicides last year.

The Biden administration has a window of opportunity to reduce the traffic of guns to Mexico and beyond. Firearms that are smuggled from the United States make their way across the continent, to Mexico as well as to Central American nations, where violence has sent waves of migrants and refugees fleeing to the United States’ southern border.

I’ve spent the last four years tracking this so-called iron river of guns, in an effort to understand why the United States and Mexico have so badly failed to stop it. The journey took me from the biggest firearms trade show in the world, in Las Vegas, to a Kalashnikov factory in Romania, to the open-air drug markets of Baltimore. The iron river to Mexico intersects with the pipeline pumping guns fromAmerican states with laxer gun laws to cities with stricter laws like Chicago, Washington and New York, which are now having a surge in homicides.

The black market for guns is intertwined with the illegal drug trade, like two venomous plants wrapped around each other. At the New York trial of Joaquín Guzmán Loera, known as El Chapo, in 2019, the prosecutor, Andrea Goldberg, described how the drug lord trafficked tons of cocaine, methamphetamines and heroin north, then moved truckloads of rifles south. “The defendant did something like purchasing the weapons or distributing the weapons, not just for himself to use, but also for sicarios [hit men] and pistoleros [gunmen] to use,” she said. “It wasn’t a bring-your-own-firearm situation.”

The black market in guns is driving murders on both sides of the border, and traffickers exploit the confusing patchwork of regulations that govern the legal firearms industry in America. Amazingly, there is no federal statute specifically prohibiting firearms trafficking in the United States.

Traffickers acquire guns through the private-sale loophole, in which people who say they are collectors can sell weapons to others without running background checks on the buyers or asking for identification. From 2009 to 2010, an American man, Hugh Crumpler III, bought 529 guns from shops and resold them at Florida gun shows, with no paperwork, for a profit. The weapons were later traced by U.S. law enforcement to a group of Latin American traffickers, and to five shootings, from Colombia to Puerto Rico. Mr. Crumpler pleaded guilty to dealing without a license and was sentenced to 30 months in prison.

President Biden should put his weight behind universal background checks to eliminate this loophole, a move the vast majority of Americans support. A 2019 NPR/PBS NewsHour/Marist poll found that 89 percent of those surveyed, including 81 percent of conservatives, said they supported background checks for all gun purchases at gun shows or other private sales. That same year, the House passed sweeping bipartisan gun-control legislation, but the Senate has yet to call it to a vote.

Another way for gangsters to get guns is by paying a “straw buyer,” or someone with a clean record, to buy a firearm. If caught, buyers convicted of lying on the form are often merely sentenced to probation. Traffickers, in turn, pay a pittance of $50 to $100 per weapon.

“They’re not going to get any jail time. What’s the deterrent factor?” says Steve Barborini, a former agent of the Bureau of Alcohol, Tobacco, Firearms and Explosives. If the sentencing guidelines were increased and straw buyers faced prison, they may think twice.

The last two methods used by traffickers are buying stolen firearms, which are often robbed from gun shops, and buying kits on the internet, known as ghost guns. There are already bills that have been proposed to the U.S. House of Representatives that would crack down on both of these.

None of the reforms would violate the Second Amendment, and they would be acceptable to many gun owners. But they have long been opposed by a powerful gun lobby fighting almost any regulation, and by Republicans in Congress blocking change.

The Biden administration has a window of opportunity, while Democrats control the House and the Senate, to move on those four measures. Hitting the black market for guns could save thousands of lives, and there is a clear path to move forward on this issue.

Drug traffickers will often adorn their guns in gold and precious stones, celebrating the tools they use to make money and spread death. I have seen a gun seized by the Mexican Army with the name of revolutionary Pancho Villa next to another with that of the fashion icon Versace. Another captured gun bore the phrase, “Only the dead have seen the end of the war.” I hope that some day soon, the living in Mexico can also see what peace really looks like.

Ioan Grillo (@ioangrillo), a contributing opinion writer, is the author of “Blood Gun Money: How America Arms Gangs and Cartels.”