The scene in 2010, when a U.S. Border Patrol agent shot 15-year-old Sergio Adrián Hernández Güereca in the culvert that separates El Paso from Juarez, Mexico. Hernández was on the Mexican side, and the agent was on the U.S. side. (AP)

The cross-border shooting of an unarmed Mexican teenager by a U.S. Border Patrol agent left behind a sympathetic victim, but the Supreme Court on Tuesday worried about extending the protections of the Constitution beyond the nation’s boundaries.

The court appeared divided on whether the dead boy’s parents have a right to sue their son’s killer in U.S. courts. Conservative justices were particularly concerned that among the unintended consequences could be an extension of rights to victims in foreign countries of drone strikes ordered from the United States.

Justice Anthony M. Kennedy, who is likely to hold the deciding vote in the case, wondered if the court should stay out of a matter best handled by the White House and Congress.

“You’ve indicated that there’s a problem all along the border,” Kennedy told Robert C. Hilliard, the Texas lawyer representing the parents of Sergio Adrián Hernández Güereca. “Why doesn’t that counsel us that this is one of the most sensitive areas of foreign affairs where the political branches should discuss with Mexico what the solution ought to be?”

[Supreme Court considers shot fired in U.S. that killed teenager in Mexico]

The court’s liberals, on the other hand, seemed to believe there was a way to give the parents a chance to sue border agent Jesus Mesa Jr. without opening the courts to all manner of lawsuits from foreign nationals who suffer at the hands of federal officials.

Justice Ruth Bader Ginsburg said the fact that Hernández was Mexican and was just inside the Mexican border when he was killed did not control the outcome of the case.

“I don’t understand all this about Mexico,” she said. “It’s the United States law operating on the United States official who’s acting inside the United States. This case has, as far as the conduct is concerned, United States written all over it.”

A 4-to-4 tie would uphold the opinion of lower courts, which said the parents do not have a remedy in U.S. courts. But if the justices are evenly divided, it is also possible they could decide to rehear the case when the court is fully staffed. President Trump’s Supreme Court nominee, Neil Gorsuch, could be confirmed in April.

The case arises from a June 2010 event in a most unusual place: the wide, concrete culvert that contains the dry bed of the Rio Grande, separating El Paso from Juarez, Mexico. The actual border runs unmarked along the middle — Justice Elena Kagan called it something of a “no-man’s land . . . kind of neither one thing nor another thing.”

Mesa was on a bike patrolling the area when Hernández and his friends played a daring game: running up the steep embankment on the U.S. side to touch the tall fence and then racing back to Mexico.

Mesa said he and other agents were under attack from a rock-throwing gang, but cellphone videos of the incident indicated that was not true. Mesa grabbed one of the other youths and then, while holding on to him, shot at Hernández, killing him as he peered from behind a bridge piling on the Mexican side.

Hilliard told the court that if Mesa had shot the youth he was holding while on U.S. territory, he could be liable. But lower courts have ruled that Hernández’s parents have no recourse because their son had no ties to the United States and was on Mexican land.

Hilliard proposed this test: “When there is a cross-border shooting involving a federal law enforcement officer on U.S. soil, and the resulting injury is in close proximity,” constitutional protections apply.

Chief Justice John G. Roberts Jr. was not impressed. “That’s a test that, surprisingly, fits the exact facts of your case,” he said. He worried about “the case of a drone strike in Iraq where the plane is piloted from Nevada.”

Justice Samuel A. Alito Jr. also noted that the court needed to think about cases beyond what Justice Stephen G. Breyer called the “sympathetic” one at hand. What if Hernández was older? Armed but with his hands up? Not in the culvert but 200 yards deeper in Mexico?

Kagan and Breyer worried about the larger implications as well.

“What are the words that we write that enable you to win, which is what you want, and that avoid confusion, uncertainty or decide these other cases the proper way?” Breyer asked Hilliard.

Later, in an exchange with Mesa’s lawyer, Randolph Ortega, Breyer seemed to answer his own question: The court could consider limiting the affected area to the culvert and border areas jointly maintained by the United States and Mexico. (Mexico supports Hernández’s parents and indicted Mesa for the killing; the United States has refused to extradite him.)

Deputy Solicitor General Edwin S. Kneedler, a department veteran arguing his first case for the Trump administration, took the same position the Obama administration had: There is no right for the parents to sue Mesa.

Kennedy asked if there were any examples in the past decade of Congress passing special laws “to compensate victims for instances somewhat like this, where the United States has either accidentally or deliberately transgressed on the rights of foreign persons?”

Kneedler said that he did not know of any but that leaving the issue to Congress, rather than recognizing new rights, was the right course.

The case is Hernández v. Mesa.