The judge hearing Mexico's lawsuit against more than half a dozen U.S. gunmakers and a firearms distributor alleging they knowingly facilitate the trafficking of weapons into the violence-plagued country peppered the plaintiff's counsel with questions Tuesday about the wider implications of the legal theory on which Mexico is basing its case.

At a hearing for a motion to dismiss the case, U.S. District Judge Dennis Saylor of the District of Massachusetts interrupted Mexico's chief counsel, Steve Shadowen, as he was delivering his opening arguments to ask whether a favorable ruling for Mexico would clear the way for other countries to sue U.S. gunmakers.