In an unprecedented case brought by the Mexican government, a federal appellate court is weighing whether a U.S. law that shields firearm manufacturers from civil liability extends to claims under foreign law that gun makers' products were criminally misused abroad.

The lawsuit accuses Smith & Wesson Brands Inc., Sturm, Ruger & Co. and others of helping facilitate the trafficking of guns across the U.S. border to criminal organizations by designing, marketing and selling weapons they could use.