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.

Justices expressed deep skepticism Tuesday about an unusual lawsuit by the Mexican government that seeks to hold major U.S. firearms manufacturers accountable for gun violence in that country.

On March 4th, hours after Donald Trump imposed tariffs of 25% on Mexican exports to the United States, Mexico’s government stood before the Supreme Court of the United States to argue that American gunmakers should be held liable for deaths caused by Mexican gangs using the weapons they manufacture.