Mexico argues that U.S. gunmakers knowingly aid and abet the illegal trafficking of firearms across the border by supplying dealers who divert weapons to the black market. The lawsuit, Smith & Wesson Brands v. Estados Unidos Mexicanos, will test the limits of the 2005 Protection of Lawful Commerce in Arms Act, a federal law shielding gun manufacturers from liability for crimes committed with their products.

Why does Mexico get to bring this type of lawsuit?

Because of a disputed exception within the PLCAA, Mexico is able to bring this case against a U.S. gun manufacturer if the country believes it has knowingly broken U.S. or state laws regulating firearms sales. Mexico argues that U.S. courts have jurisdiction because the alleged harm, cartel violence, is directly tied to the actions of gunmakers and that their distribution practices violate laws intended to prevent illegal gun trafficking.

Specifically, the Mexican government claims that several practices by the gun manufacturers, which are legal under U.S. gun laws, constitute a “proximate cause” for firearm violence in Mexico, despite Smith & Wesson’s denial of these alleged links.

Mexico argues that Smith & Wesson and other manufacturers knowingly facilitate illegal gun trafficking by designing military-style weapons favored by cartels, marketing them in ways that appeal to criminal groups, and failing to implement safeguards in their distribution networks to prevent firearms from reaching illicit markets. The lawsuit contends that these actions make the companies complicit in the violence fueled by trafficked U.S. guns, even if they operate within legal boundaries.

The justices will be tasked with answering two main questions surrounding the allegations from Mexico: Whether gun manufacturers are “aiding and abetting” illegal firearm trafficking through their sales practices, and whether the manufacturers can be held liable for violence caused by third parties, in this case, Mexican drug cartels.

Mexico “faults the defendants for producing common firearms like the AR-15; for allowing their products to hold more than ten rounds; for failing to restrict the purchase of firearms by regular citizens; and for refusing to go beyond what American law already requires for the safe production and sale of firearms,” according to the complaint.

The federal district court that initially took the lawsuit dismissed Mexico’s action as barred under PLCAA. However, the U.S. Court of Appeals for the First Circuit, a predominantly Democratic-controlled appeals court, reversed and said Mexico could bring the case under the 2005 statute, prompting an appeal and bringing the case to the justices.

If the Supreme Court sides with Smith & Wesson, it could effectively shut down future lawsuits against gunmakers for any event, including school shootings.

If the justices rule in Mexico’s favor, it could open the door to a wave of litigation targeting the firearms industry, a move that pro-gun groups say would jeopardize Second Amendment protections by putting gunmakers in the crosshairs of costly and potentially bankrupting litigation.

The Supreme Court’s eventual ruling could also have far-reaching consequences beyond gun manufacturers, such as litigation against social media companies, fossil fuel firms, and pharmaceutical manufacturers facing lawsuits over their products’s societal effects.

Democratic-led states and left-leaning groups side with Mexico

The case has inspired sharp ideological battle lines. Left-leaning groups such as March for Our Lives and the Giffords Law Center back Mexico’s lawsuit, arguing that gunmakers must be held accountable for what they see as reckless sales practices.

Meanwhile, Massachusetts, several other Democratic-led states, and Washington, D.C., filed an amicus brief supporting Mexico.

“While Congress sought through PLCAA to limit novel forms of liability for blameless gun manufacturers and sellers whose guns and ammunition are used by third parties to inflict harm, Congress did not wish to extinguish liability for wrongful conduct by manufacturers and dealers themselves,” the pro-Mexico petitioners argued in a friend-of-the-court brief.

Republican groups say a ruling against gunmakers would hamper Second Amendment

On the other side, pro-gun groups, including the National Rifle Association and Gun Owners of America, have sided with the manufacturers, warning that a ruling against them would threaten the Second Amendment. Montana and a coalition of Republican-led states and lawmakers such as Sen. Ted Cruz (R-TX) filed briefs urging the Supreme Court to reject Mexico’s claims.

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“The district court understood as much and dismissed Mexico’s action as barred by PLCAA. The district court properly rejected Mexico’s arguments that because its alleged injuries occurred outside the United States and because it is a foreign sovereign plaintiff, PLCAA was categorically inapplicable to this lawsuit,” according to Cruz’s brief, which was joined by 25 other Republican lawmakers.

The justices’ questions during arguments on Tuesday at 10 a.m. EST will offer clues about how they may rule in a case with enormous stakes for both the firearms industry and broader corporate accountability battles.