The Supreme Court will hear arguments next week in a Fourth Amendment case, Hernandez v. Mesa. The facts of the case are simple. At the border that separates El Paso, Tex., from Ciudad Juárez, Mexico, a U.S. border patrol agent named Mesa shot and killed a Mexican citizen named Hernandez. The bullet itself crossed the border, as Mesa was on U.S. land and Hernandez was on Mexican land. A subsequent lawsuit was filed by Hernandez’s parents, as successors-in-interest to his estate, alleging excessive force under the Fourth Amendment.

The cert petition articulated two questions to be decided:

Does a formalist or functionalist analysis govern the extraterritorial application of the Fourth Amendment’s prohibition on unjustified deadly force, as applied to a cross-border shooting of an unarmed Mexican citizen in an enclosed area controlled by the United States?

May qualified immunity be granted or denied based on facts—such as the victim’s legal status— unknown to the officer at the time of the incident?

When the court granted cert, the court added a third question drafted by the court itself: “Whether the claim in this case may be asserted under Bivens v. Six Unknown Fed. Narcotics Agents, 403 U. S. 388 (1971).”

Here are a few thoughts about the case.

One of the most important questions for the future of the Fourth Amendment is whether non-U.S. persons get Fourth Amendment rights abroad. As I explained in my recent article, “The Fourth Amendment and the Global Internet,” 67 Stan. L. Rev. 28 (2015), the basic structure of what kind of Internet surveillance is permitted hinges on the question.

Under the rule of the majority opinion in Verdugo-Urquidez — the so-called formalist approach — you get one framework with some significant uncertainties but a lot of results settled. On the other hand, under Justice Anthony Kennedy’s “impracticable and anomalous” test — the so-called functional approach — no one really knows what the Fourth Amendment would look like in the context of global network surveillance. And because those cases come up for litigation so rarely, it would take many years for courts to figure out the answers (by which time the technology may have changed anyway).

From that perspective, the odd part about Hernandez v. Mesa is that it asks the court to decide between the formalist and functionalist approaches in a setting that appears to implicate almost none of the real stakes of the answer. The facts of a shooting across the border are like a law school exam. They raise interesting questions, but the context seems pretty idiosyncratic. In contrast, the application of the functionalist or formalist approach has a massive day-to-day impact on global Internet surveillance. It’s there, not in the context of a cross-border shooting, that the Fourth Amendment question in Hernandez seems to matter most.

Hernandez’s brief argues that the court can and should apply or not apply individual parts of Fourth Amendment doctrine to non-citizens abroad depending on whether doing so would be “impracticable or anomalous.” But I don’t see how this is at all workable. As I explain in a forthcoming article, Fourth Amendment rules are deeply path-dependent. The rules on what is a search impact the rules on what is reasonable, and vice versa; and they together impact the available remedies, and the remedies have an impact on them. In an area of law that is as exquisitely fact-sensitive as the Fourth Amendment, I don’t know how you could tell whether a particular doctrine’s application would be “impracticable or anomalous.” Assuming you had an empirical way to answer that in the abstract, the answer would depend on what the other doctrines are, and without knowing if their application to non-citizens abroad would be “impractical and anomalous, I don’t know how you could tell.

Hernandez tries to avoid these problems by suggesting a very narrow holding. The reply brief advocates the following narrow rule: “[T]he prohibition on unjustified deadly force applies at (and just across) the border, at least when a law-enforcement officer on U.S. soil fires his weapon at close range.” But this attempted narrowing just makes the problem much worse. It’s bad enough to figure out how the “impracticable or anomalous” framework should apply doctrine by doctrine. Hernandez seems to want to apply it fact pattern by fact pattern, imposing some essentially arbitrary definition of the relevant set of facts.

Think closely about Hernandez’s proposed rule. In his “far narrower” view, the rule of extraterritorial liability advocated for in this case would apparently apply not to all excessive-force claims brought by non-citizens, but only to claims of “unjustified deadly force” brought by them; not outside the United States generally, but only at the specific location of “at (and just across) the border”; and maybe (although maybe not!) only to the narrower circumstance when the U.S. officer “fires his weapon at close range.” The phrasing of the question presented in the cert petition suggests another possible limitation: Maybe it applies only to shooting a person who is “an unarmed Mexican citizen.” As to the rule that would apply to any other facts, well, hey, courts will have to figure those out over time.

That seems kind of nuts to me. If any court can pick the set of facts over which a proposed rule of extraterritorial application controls, the result will be that any Ninth Circuit lower-court judge can just pick the result he or she wants in any case. If Judge Reinhardt has a case and wants to hold the defendants liable, he can draw the category of facts in a stylized way so that application of the Fourth Amendment doesn’t seem “impracticable.” If another judge wants to rule against the plaintiffs, she can draw the category of facts differently so that it does. That strikes me as really problematic.

All of which is to say that I hope the court sticks with the majority opinion in Verdugo-Urquidez. Not only is it relatively clear, but also I personally tend to think it is based on a persuasive social contract approach to rights.

The Fourth Amendment issue in Hernandez is made more interesting by a practical point: It’s not clear whether other members of the court beyond Kennedy agree with using the “impracticable or anomalous” test in the Fourth Amendment context. It sometimes happens that other justices are willing to sign on to a Kennedy opinion with reasoning that they don’t particularly agree with, if it’s needed to get to a five-justice majority. But that doesn’t always happen, and it could happen either way in this case (with Kennedy applying the “impractical or anomalous” test in favor of either the petitioners or respondents). If the court reaches the merits, it will be really interesting to see where the votes will come out on that issue.

Finally, it’s not at all obvious that the court will reach the Fourth Amendment merits. The court added the Bivens question on its own, and the Solicitor General’s Office brief took the hint and made that the lead argument in its brief. The Bivens issue takes up fully 20 pages of the argument section in the government’s brief, as compared with 15 pages for the Fourth Amendment merits and eight pages for the qualified-immunity issue. We’ll have to wait and see which issue draws the justices’ attention.

As always, stay tuned.