[Analysis] Mexico gun lawsuit dismissed by U.S. Supreme Court, but legal pathways remain open

In a new blog post for Just Security, researcher León Castellanos-Jankiewicz analyses the recent U.S. Supreme Court decision that unanimously ruled Mexico’s lawsuit against seven U.S. gun manufacturers and one distributor is barred by the immunity they enjoy under the Protection of Lawful Commerce in Arms Act (PLCAA). The ruling reversed an earlier decision that had permitted some of Mexico’s claims to move forward. Castellanos-Jankiewicz: “Ultimately, Mexico’s lawsuit has shifted the conversation around corporate responsibility for wrongful arms sales—a victory that extends beyond any single court ruling.”

On June 5, the U.S. Supreme Court unanimously dismissed Mexico's lawsuit against American gun manufacturers Smith & Wesson Brands Inc. v. Estados Unidos Mexicanos, finding that federal immunity protections under the Protection of Lawful Commerce in Arms Act (PLCAA) barred the claims.

While Mexico's legal strategy failed, the Court's reasoning provides important guidance for future litigation strategies, writes Asser Institute researcher León Castellanos_Janckiewicz, who supported Mexico’s case through an amicus brief, in his Just Security blog titled “SCOTUS Rules for Gun Manufacturers in Mexico Suit But Denies Blanket Immunity”.

Mexico’s original complaint was filed in 2021 and argued that the companies aid and abet gun traffickers in smuggling weapons into Mexico through irresponsible manufacturing, marketing, and distribution practices. . Mexico’s legal challenge addressed a significant transnational security issue, with estimates that between 200,000 and 1 million US firearms are trafficked into Mexico annually, substantially contributing to cartel violence and imposing considerable costs on Mexican law enforcement. 

“Active and culpable participation”
As reported by Castellanos-Jankiewicz, the Supreme Court's analysis focused on the aiding and abetting exception to PLCAA immunity, requiring plaintiffs to demonstrate "active and culpable participation" in facilitating illegal transactions. Counsel for Mexico noted that by constantly supplying red-flag sellers, the defendant manufacturers had an “active, culpable participation” in aiding and abetting cartel violence.

The justices, however, found Mexico's allegations insufficient, characterising the manufacturers' conduct as too passive  rather than amounting to deliberate assistance. Critically, the Court emphasised that successful claims must identify specific criminal transactions and demonstrate manufacturers' direct engagement with problematic dealers.

Future cases
According to Castellanos-Jankiewicz, this procedural dismissal notably avoids granting blanket immunity to gun manufacturers. The Court outlined clear evidentiary requirements under aiding and abetting for future cases, particularly regarding the relationship between manufacturers and downstream distributors engaged in illegal sales.

Castellanos-Jankiewicz writes: "While Mexico’s claims were set aside, the Court laid out new pathways to accountability, providing a clearer roadmap of which legal strategies are likelier to succeed. 
Moreover, the Court did not accept that gun companies have blanket immunity. Aiding and abetting liability remains a possibility if arms manufacturers have an active and culpable participation in facilitating arms trafficking.

The lawsuit also has important dissuasive effects. About 83 percent of crime guns in Mexico are traced to small U.S. retailers, and these sellers now face real incentives to reassess their business practices and mitigate legal risk. Ultimately, Mexico’s lawsuit has shifted the conversation around corporate responsibility for wrongful arms sales—a victory that extends beyond any single court ruling.”

Mexico continues pursuing accountability through a separate Arizona lawsuit against firearms dealers directly, while diplomatic efforts to address transnational arms trafficking remain ongoing. 

Read the full publication

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About León Castellanos-Jankiewicz
Dr León Castellanos-Jankiewicz is senior researcher in International Law at the Asser Institute, and supervisor of the International Law Clinic on Access to Justice for Gun Violence at the University of Amsterdam Faculty of Law. His work focuses on the human rights implications of irresponsible arms trade and the history of public and private international law. Castellanos-Jankiewicz regularly advises governments on arms export policies, and leads the project on 'Enabling Civil Society Efforts to Address the Misuse, Diversion and Abuse of Arms Exports in Latin America' within the Asser Institute, which was awarded a competitive grant by the U.S. State Department (2023-2025).