Can the family of a slain Mexican teenager sue the federal agent who shot him across the U.S.-Mexico border for damages? The U.S. Supreme Court did not answer this question on Monday, instead opting to send a case back to a lower court.

The case centers on a larger question: whether the Constitution extends protection to an individual who is killed on foreign soil, even though that person is standing just a few yards outside the United States.

It also tests a long-held doctrine, called a Bivens action, in which plaintiffs are permitted to sue federal officials for breaking constitutional law. But that doctrine had never been applied outside the boundaries of the United States.

In oral arguments in February, some justices were concerned that making U.S. agents liable for their actions taken in a foreign nation could be extended to, say, a house full of noncombatants killed by a U.S. drone strike in Pakistan.

Bob Hilliard, the Texas attorney for the Mexican teen's family, argued that a decision could be crafted in such a way as to only address the legally vague U.S.-Mexico borderlands, where this fatal shooting took place.

In 2010, some Mexican youths were playing a game of dashing across a concrete riverbed between El Paso, Texas, and Juarez, Mexico, to touch the U.S. border fence. A Border Patrol agent, Jesus Mesa Jr., arrived on a bicycle and detained one of the youths. Claiming he was the target of rock throwers, Mesa — who was standing on the U.S. side — pulled his handgun and shot 15-year-old Sergio Hernandez Guereca in the head as he peeked out from behind a concrete pillar on the Juarez side of the international culvert.

The family claimed the agent violated Hernandez's Fourth and Fifth Amendment rights against deadly force, even though he was a noncitizen. Hilliard, the Corpus Christi lawyer representing Hernandez's family, warned against creating "a unique no-man's land — a law-free zone in which U.S. agents can kill innocent civilians with impunity."

The FBI cleared Agent Mesa of wrongdoing, and the government has defended his immunity from civil lawsuits.

Hernandez had been arrested twice in the U.S. for human smuggling and released because he was a juvenile, but the agent didn't know that when he shot him under the left eye.

A Court of Appeals had ruled that the Border Patrol agent, Mesa, had qualified immunity, which means he cannot be sued. But in today's opinion, the justices vacated that ruling.

The Supreme Court said the lower court made a mistake when it found Mesa had qualified immunity. The lower court's rationale stressed that Hernandez was not a U.S. citizen, which the justices say that Mesa did not know when he shot him.

The court also stated that another case that it decided last week, Ziglar v. Abbasi, could have bearing on Hernandez v. Mesa, which the lower court would not have considered.

The final decision has the potential to affect not only the Hernandez family, but several other Mexican families who were waiting to file civil suits against federal officers for cross-border shootings of their loved ones.

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