As President Donald Trump pressures Mexico to address the flow of migrants and drugs heading north into the United States, the Supreme Court is set to hear arguments Tuesday in a major appeal about one thing that’s crossing the border toward Mexico: guns.

Do U.S. arms manufacturers bear responsibility for the guns fueling cartel violence in Mexico? Mexico is arguing that case before the Supreme Court.

Supreme Court justices expressed skepticism as Mexico attempted to hold American gun companies responsible for drug cartel violence.