Sarah A. Seo is an associate professor of law at the University of Iowa College of Law, where she teaches criminal procedure and legal history.

On Monday, the Supreme Court sidestepped the question of whether constitutional protections reached this concrete culvert in Mexico, where Sergio Hernandez was shot by a U.S. border agent. (YURI CORTEZ/AFP/Getty Images)

On Monday, the Supreme Court punted in the case Hernandez v. Mesa. The parents of Sergio Hernandez sued U.S. border agent Jesus Mesa Jr. for fatally shooting their son. Sergio, 15 years old in 2010, was playing with three other boys in the concrete culvert that was once the Rio Grande and now marks the boundary between the United States and Mexico. Many of the facts from that day are disputed. But both parties agreed on this: Mesa was on U.S. soil when he fired the shot, and Sergio was standing on Mexican ground when the bullet hit him in the head.

The question for the Court to decide was whether Sergio’s parents could bring a lawsuit in the United States against Mesa for conduct that violates the U.S. Constitution when the victim is not a U.S. citizen and not on U.S. territory. The Court of Appeals for the Fifth Circuit had decided that the Hernandez family could not because, among other reasons, someone who was not a U.S. citizen, not in the United States, and who had no “significant voluntary connection” to the United States did not enjoy the Fourth Amendment right against unjustified deadly force.

The Supreme Court avoided having to decide the constitutional issue by asking the Fifth Circuit to reconsider the case on a different ground: whether courts could permit this lawsuit absent a law that explicitly provides for it.

This decision makes little sense. Even if the Fifth Circuit were to decide that the case can proceed, it had already determined that there was no constitutional violation in this case. The Hernandez family still loses. The opinion would have made more sense had the Court also decided that the lower court was wrong on the Fourth Amendment. The Court declined to do so and essentially asked the Fifth Circuit to provide a different reason for dismissing the Hernandez family’s lawsuit.

The Supreme Court’s attempt to sidestep the constitutional question suggests that the Justices encountered a challenge they did not want to tackle. At oral argument, the Hernandez family’s lawyer, Robert Hilliard, had difficulty convincing a sympathetic, but mostly skeptical Court that the territorial problem should not block their pursuit of justice for their son. At first, Hilliard argued that border cases were different.

If that were the case, however, then the Justices wanted to know: What made a border case different from the U.S. military launching a drone strike in Iraq from a plane piloted in Nevada? If the Court permitted Sergio’s parents to sue, then couldn’t victims of the drone strike also sue the U.S. government? Hilliard struggled to give an answer that satisfied all of the Justices.

Halfway into his argument, Hilliard tried a new approach. He claimed that the United States exerted “some degree of control” over the culvert, including the area that was not formally on the U.S. side of the border. To this, Chief Justice John Roberts asked the logical follow-up question: Did the government of Mexico agree with the assertion that the jurisdiction of the United States extended beyond the Mexican border? In an attempt at clarification, the lawyer restated his claim: Even when the Border Patrol stays on U.S. land, it nevertheless “projects authority outward.”

This argument sounds laughable in a court of law, where borders determine sovereignty. But the lawyer was articulating an idea that historians have been studying for some time: the concept of borderland.

A borderland is an area where two or more empires, nations or societies meet. Borders may be clearly defined on maps. But for people who live in a borderland, power is constantly negotiated and claimed. This may result in a mutually beneficial arrangement, what historian Richard White calls a “middle ground” where cultures intersect and blend through trade and intermarriage.

At other times and places, borderland people submit to de-facto rulers who live among them rather than in faraway capitals of power. And those de-facto rulers aren’t always who you’d expect them to be. For instance, in “The Comanche Empire,” Pekka Hamalainen argued that from 1750 to 1850, it was the Comanche — not the United States, not Spain, not a later independent Mexico — that dominated the Southwest economically, politically and militarily.

Cultural interchange existed in this borderland as well. But one group dominated the others through violence and exploitation. The Comanche might not have called themselves an empire, but they exercised imperial power, including demanding — and collecting — regular tribute from the Euro-American settlers.

Hilliard was grasping at this concept of borderland when suggesting that the U.S. Border Patrol “projects authority outward.” True, the United States does not have sovereignty over Mexican territory, and the border today is more established with concrete culverts and immigration checkpoints. Laws prohibiting our agents from crossing the border reflect the formal boundaries that are drawn on maps.

But it is also true that agents wield tremendous power in the borderland that lies to our south and to Mexico’s north. The increasing frequency of cross-border shootings reflects this reality. American border agents may not be the Comanche warriors of centuries past, but their use of deadly force seems more real than the borders of “an engineer’s ‘imaginary line,’ perhaps thousands of miles long, but having ‘no width,’” as Justice Stephen Breyer quoted in his dissent.

Hernandez v. Mesa was the first time that the Supreme Court had confronted a completely extraterritorial application of our Constitution. But it may not be the last. By punting on this case, the Court indicated that it did not want a case that decides whether the Constitution can follow a border agent’s bullet to also determine whether, for instance, non-U.S. citizens can challenge global Internet surveillance. In due time, the Court will have to decide whether our Constitution will reflect reality on the ground or reality on paper.