A U.S. judge on Tuesday questioned whether allowing Mexico to sue U.S. gun manufacturers for facilitating the trafficking of weapons to drug cartels would open the door to other countries suing them, including Russia over firearms used by Ukrainians in the ongoing war.

U.S. District Judge F. Dennis Saylor in Boston raised that prospect as he weighed whether to dismiss Mexico’s $10 billion lawsuit seeking to hold gunmakers including Smith & Wesson and Sturm, Ruger & Co. responsible for a deadly flood of weapons across the border.

Mexico in a lawsuit filed in August accused the companies of undermining its strict gun laws by designing, marketing and distributing military-style assault weapons in ways they knew would arm drug cartels, fueling murders and kidnappings.

It said over 500,000 guns are trafficked annually from the United States into Mexico, of which more than 68 percent are made by the gunmakers it sued, which also include Beretta USA, Barrett Firearms Manufacturing, Colt’s Manufacturing Co and Glock Inc.

“They know how criminals are getting their guns,” Jonathan Lowy, a lawyer for Mexico, argued during the 90-minute virtual hearing. “They could stop, and they choose to be willfully blind to the facts.”

But Saylor questioned whether Mexico’s stance would mean the protections gunmakers typically enjoy under the federal Protection of Lawful Commerce in Arms Act (PLCAA) from lawsuits over their products’ misuse is “completely hollow.”

He asked why if Mexico could sue the gunmakers, other countries could not, too, such as Italy over mafia killings, Israel over attacks by Palestinian militant group Hamas, or even Russia over the deaths of its soldiers in Ukraine if the companies’ guns were used.

“If Ukrainians are using United States-manufactured military weapons or Smith & Wesson revolvers for that matter to defend themselves, can the government of Russia come in and say, ‘you have caused us harm’?” he asked. “I mean, why not, if your theory is right?”

Steven Shadowen, another lawyer for Mexico, said other foreign counties could sue, too, if they met the requirements, though he said U.S. courts could refuse to hear a case if it presented a political question.

But Andrew Lelling, a lawyer for Smith & Wesson, said it would be “absurd” to conclude the federal law only bars lawsuits over injuries in the United States and not Mexico’s allegations over the trafficking of guns to Mexican criminals.

He said it was too much of a reach for Mexico to sue the companies over gun sales that were legal in the United States to wholesalers who in turn sold them to retailers before criminals smuggled them.

“They would have to argue that Congress intended for this robust statute to apply if an independent criminal actor shot somebody in San Diego but not if he slips over the border and shoots somebody in Tijuana,” Lelling said.

Alejandro Celorio, the Mexican foreign ministry’s legal counsel, said the court’s resolution would likely take weeks, and noted that the complexity of the case made a nuanced ruling, rather than a simple “yes or no,” more likely in the end.

Speaking in a video conference, Celorio said if the court ruled against Mexico, the government would likely appeal. A negotiated settlement was “always an option,” he added, but stressed Mexico had no plans to change its strategy for now.

(Reporting by Nate Raymond in Boston, Editing by Alexia Garamfalvi and Alistair Bell)