The Supreme Court gravitated toward the American firearm industry Tuesday in its fight to end a $10 billion lawsuit brought by the Mexican government over claims the gunmakers are fueling cartel violence. The case has become a major battle over the scope of the Protection of Lawful Commerce in Arms Act (PLCAA), which has provided broad immunity to gunmakers for two decades despite gun control activists’ attempt to repeal it. At oral arguments Tuesday, the justices posed piercing questions to Mexico’s attorney about claims the country’s lawsuit falls under an exception to the 2005 law, raising concerns that accepting that position would cause a flood of litigation against the gun industry.