A federal appeals court says a U.S. Border Patrol agent who fired his gun in Texas and fatally wounded a teenager across the Mexican border cannot be sued by the teen's family.

The 5th U.S. Circuit Court of Appeals ruled Tuesday in the case of 15-year-old Sergio Adrian Hernandez. He was killed by agent Jesus Mesa  in 2010. The Justice Department has said Mesa was trying to stop illegal border crossings and fired after he came under a barrage of rocks.

The appeals court voted 13-2 to uphold a federal district judge's dismissal of the family's claims. The case involved questions of whether and when constitutional rights afforded American citizens extend to non-citizens outside the nation's boundaries.

The appellate court majority said the case involved issues of diplomacy and national security.