Amid escalating tensions with its northern neighbor over immigration, drug smuggling, tariffs and other matters, Mexico is about to appear in the U.S. Supreme Court to defend a lower-court ruling allowing a major lawsuit against members of the U.S. gun industry to proceed.

Mexico sued seven firearms manufacturers and one wholesaler in 2021, alleging that they deliberately market and sell guns that make their way to drug cartels, fueling an epidemic of violence.

"Mexico has one gun store in the country and has extremely tough gun laws," says Jonathan E. Lowy, the president of Global Action on Gun Violence, a Washington legal and advocacy group that is helping represent Mexico. "Yet it has one of the worst gun violence problems in the world. That is almost entirely the result of the U.S. gun industry, which contributes to the illegal trafficking of hundreds of thousands of guns into Mexico every year."

In the 2021 civil lawsuit, Mexico claimed that nearly half of all firearms recovered at Mexican crime scenes are made by the seven U.S. firearms manufacturers named among the defendants. The suit is a common-law action seeking some $10 billion in damages and various forms of injunctive relief. It has two significant claims: The defendants "aided and abetted" unlawful firearms sales to gun traffickers, and those sales were a "proximate cause" of Mexico's harm. The suit says the defendants supply dealers known to disproportionately sell guns that end up in Mexico and in the hands of the cartels.

"This is a massive problem that the United States has recognized," Lowy says. "Mexico believes that the most effective way to address this problem is at the source, by shutting the spigot on this illegal gun pipeline."

A federal district court in Massachusetts dismissed the suit, ruling that it was "exactly" the "type of action" that a 2005 federal law, the Protection of Lawful Arms in Commerce Act, was meant to prevent. PLCAA was a response to a growing number of lawsuits seeking to hold the industry liable for mass shootings and other gun violence. It bars most civil actions "resulting from the criminal or unlawful misuse of a qualified product by the person or a third party."

But the law also provides that manufacturers and sellers can be held civilly liable when they "knowingly violate a state or federal statute applicable to the sale or marketing" of firearms, where the "violation was a proximate cause of the harm for which relief is sought."

The 1st Circuit U.S. Court of Appeals in 2024 reversed the district court and revived Mexico's suit. The appellate court held that the suit plausibly alleges that the defendants aided and abetted statutory violations that proximately caused harm to Mexico.

The defendants appealed that decision to the Supreme Court in Smith & Wesson Brands Inc. v. Estados Unidos Mexicanos. The case will be argued on March 4.

Noel J. Francisco, a Jones Day partner and former U.S. solicitor general during President Donald Trump's first term, will argue for the gun industry defendants. He says in a brief that Mexico's suit would, if successful, ban assault weapons; limit the size of ammunition magazines; and limit how firearms are sold in the United States.

"Mexico's alleged injuries all stem from the unlawful acts of foreign criminals," Francisco says in the brief. "It is hard to imagine a suit more clearly barred by PLCAA." (Francisco declined the ABA Journal's interview request.)

The case has broad implications both in the United States and across its southern border. Mexican President Claudia Sheinbaum in early February asked Trump, amid conversations about border security and the U.S. president's threat to impose tariffs, for help in stopping the flow of U.S. guns into her country. She has said Trump agreed to help.

But after the Trump administration this month designated eight Latin American drug trafficking organizations, including six in Mexico, as terrorist organizations, Sheinbaum threatened to expand its lawsuit over guns to include a charge of U.S. complicity with organized crime.

The Supreme Court case has obvious national significance and foreign-policy implications for the U.S. and Mexico, so it was surprising to some observers that the U.S. solicitor general's office took no position.

Most briefing in the case was due by Jan. 17, just before the change in presidential administrations.

Timothy D. Lytton, a law professor at Georgia State University and the editor of the 2005 book Suing the Gun Industry: A Battle at the Crossroads of Gun Control and Mass Torts, says that perhaps even the administration of President Joe Biden "did not want to take on the firearms industry on civil litigation."

"It's a sticky issue," says Lytton, who joined an amicus brief by professors that supported neither party but argues for a robust reading of the proximate cause exception to PLCCA's protections. "America is basically blaming Mexico for illegal immigration and the passage of fentanyl from the south, and Mexico is blaming the United States for the traffic in firearms from the north."

David Pucino, the legal director of the Giffords Center to Prevent Gun Violence, one of several gun control groups to support Mexico, says the case is significant because it marks the first time the Supreme Court will interpret PLCCA.

"The gun industry faces a really strong decision against them," he said, referring to the 1st Circuit ruling. "They're trying to leverage this appeal in the Supreme Court to get a decision that shrinks their liability and makes it harder to hold them accountable."

Mexico argues in its merits brief that its case rests on "basic proximate-cause and aiding-and-abetting principles," and that at this early stage, it has plausibly pled facts that bring its suit within the exception from PLCCA's protections.

Still, it repeats some of the details from its complaint, including that some suppliers design weapons to cater to the Mexican cartels, such as Colt's Manufacturing Company's Super "El Jefe" pistol, which refers to cartel bosses, and the "Emiliano Zapata 1911" pistol, which honors the Mexican revolutionary hero.

One of the industry's allies, the Second Amendment Foundation, says in an amicus brief that manufacturers may use these references "to market their firearms to law-abiding citizens who are interested in buying firearms—including veterans and Hispanic Americans."

The gun industry defendants have the support of their trade association and other business groups and gun rights organizations.

"A private right to keep and bear arms inherently depends on the ability of citizens to obtain them in the first place," says the amicus brief of the National Association for Gun Rights.

The National Rifle Association of America, referring to tight restrictions on legal gun ownership in Mexico, says in its amicus brief: "The Mexican government seeks to extinguish the Second Amendment as it extinguished the Mexican constitutional arms right."

The gun industry defendants themselves stress arguments more specific to PLCCA.

Mexico's case "rests on independent act after independent act, crime after crime, spanning an international border, all to link [the defendants'] conduct in this country to the mayhem south of the border," Francisco argues in his merits brief. "That stretches proximate cause far beyond anything this court has seen."

And "manufacturers and suppliers are not guilty of 'aiding and abetting' downstream crimes when they do nothing but make and sell lawful products in the ordinary course," the brief says.

The case has important implications not just for Mexico but for the United States.

A lawsuit stemming from the 2012 mass shooting at Sandy Hook Elementary School in Newtown, Connecticut, which killed 20 young children and six adults, was able to pierce PLCCA's liability shield in a 2019 state court decision. That ruling led to a $73 million settlement in 2022 between Remington, the maker of the AR-15 rifle used in the shooting, and nine families.

Several states have amended their public nuisance or consumer protections statutes in ways meant to bring them into the exceptions of PLCCA's protections for the gun industry, and they are watching the outcome of this case.

Meanwhile, Mexico argues that its case is not about the right to bear arms in the United States.

"This case is also at the beginning of a long road," the nation says.

Lowy, on the Global Action on Gun Violence group that is helping represent Mexico, says that at this stage, its allegations must be accepted as true and the industry's arguments would sharply limit a theory of liability that is used regularly in criminal and civil litigation.

"We are confident the [Mexican] government can and will prove what it has alleged and more," he said. "The gun manufacturers have every right to present their own evidence and dispute our allegations. But not at this stage."