This entry is cross-posted from USvJones.com, a website of commentary by law professors about the implications of the Supreme Court’s decision in, yes, U.S. v. Jones.

I would like to do something perverse with the Supreme Court’s decision in United States v. Jones: focus on what the court actually held. Scholarly attention has focused on Justice Sotomayor’s concurrence and Justice Alito’s opinion concurring in the judgment, and their apparent willingness to embrace a mosaic theory of sustained observation, and to rethink the third-party doctrine. But in its own way, Justice Scalia’s majority opinion raises just as many deep questions as the concurrences do.

By grounding the Fourth Amendment “search” in property law—in particular, the sleepy backwater tort of trespass to chattels—the Court follows what Orin Kerr calls the “positive law” model of Fourth Amendment protection. The scope of one’s privacy rights is defined in part by the scope of one’s property rights. But only in part. The Court’s opinion, however, suggests that some trespasses will not be searches, and that some searches would not be actionable under trespass law. The divergences are instructive, both about the Fourth Amendment and about property law.

Jones raises four kinds of questions about trespassory searches:

• What things are protected?
• What activities in relation to those things are prohibited?
• What counts as valid consent to use the things?
• What consequences or circumstances are needed to make a “technical trespass” actionable?

In each case, it turns out, Scalia’s opinion for the Court raises basic conceptual issues about the nature of trespass.

First, start with the things protected from trespass. The Fourth Amendment is straightforward on this score: it protects “right of the people to be secure in their persons, houses, papers, and effects.” This sounds simple enough: it includes the body (“persons”), real property (“houses”), and personal property (“papers” and “effects”). Concerned about a search? There’s a tort for that. Battery protects the person, trespass protects real property, trespass to chattels protects personal property.

But here is the first place where the post-Jones Fourth Amendment law of trespassory searches diverges from trespass law. The Court reaffirms that a trespass to open fields is not a search, because the Amendment describes only “houses.” Trespass is not so restricted: in the canonical case of Jacque v. Steenberg Homes, the Supreme Court of Wisconsin upheld a $100,000 punitive damage award for a trespass over a vacant snow-covered field.

Among the ironies of this holding is that the Fourth Amendment may now protect personal property more stringently than it does real property. Unlike “houses,” which the Court reads to exclude open fields, “effects” is a catch-all term for all personal property. But historically, trespass to land was a more muscular tort than trespass to chattels; common law has a “special respect for land ownership.” The Court cites Entick v. Carrington for the absoluteness of trespass to land:

[O]ur law holds the property of every man so sacred, that no man can set his foot upon his neighbour’s close without his leave; if he does he is a trespasser, though he does no damage at all; if he will tread upon his neighbour’s ground, he must justify it by law.

Second, consider the nature of the activities that make a non-owner’s use of those things problematic. In Jones itself, the police attached a tracking device to Jones’s car. This was an extended touching of the car by an object that did not significantly affect the car itself. The Court uses a variety of language to describe the genus of conduct of which this is a species: the government “occupied” Jones’s property, this was an “invasion” or an “intrusion.”

This last language (repeated six times in the majority opinion) is telling. It comes from a phrase in Justice Brennan’s concurrence in another tracking-device case, United States v. Knotts, “physical intrusion of a constitutionally protected area.” The idea is profoundly spatial: like a home, a car defines a space, into which the police may not extend so much as an arm without triggering the Fourth Amendment. (The most amusing portions of Jones involve Justice Scalia and Justice Alito butting heads over the plausibility of a “a constable’s concealing himself in the target’s coach.”)

But most personalty is much smaller; it would be odd to speak of “intruding” into a wallet or a jacket. Indeed, slapping a GPS device on a car is more of an extrusion than an intrusion. Justice Sotomayor’s concurrence says the government “usurped” the car, which focuses on the misuse of property rather than the entry into a space it defines.

This issue is most likely to play out in surprising ways when it comes to the question of what kinds of contact constitute a trespass. The line between tangible and intangible contacts is a problematic one in property law, as Justice Alito’s concurrence observes. For real property, a series of cases ask whether dust, vibrations, or radiation can sound in trespass, or whether they must be raised as nuisances. Radiation, in particular, will be of great interest for advanced surveillance technologies: imagine an active version of of the thermal scanning devices at stake in Kyllo v. United States. But land has other boundaries as well. If we’re committed to an originalist understanding of trespass, then the ad coelum rule presumably applies, which means drones need to stay out of the column of airspace above the suspect’s property (or at least the column above her house).

For personal property, electronic communications with computers have been successfully pleaded as trespasses to chattels, and the modern trend is that such intangible intrusions are actionable (at least when they lead to damages, as discussed below). This trend may or may not matter for an originalist, but it does suggest that certain kinds of electronic surveillance may be problematic even without reference to an expectation of privacy. When the police log in to a suspect’s computer, the “intrusion” is virtual, but there is also inarguably an intangible contact with the computer treated as a chattel.

Third, there is the problem of consent. One axis here is the well-known Fourth Amendment problem of who is entitled to consent to or object to a search. The Court distinguished a previous tracking-device case, United States v. Karo by holding that there the tracker had been installed before the chattel came into the possession of the suspect. Justice Alito, in challenging the trespassory search theory, pointed to the variations among state community-property laws as affecting who will have property rights in an object.

But there is another problem lurking here. In Karo, the initial installation was not the only relevant conduct. If the suspect had pleaded instead that the continuing attachment of the device was an ongoing violation of “the dignitary interest in the inviolability of chattels,” this would appear to be a good plea of trespass to chattels. So perhaps the suspect’s initial acceptance of the chattel with the device attached is to be treated as consent, which the suspect could revoke at any time. But this is a stretch: we do not ordinarily say that one gives consent to trespasses of which one is completely unaware.

This brings us into the deeply murky area of consent obtained under false or misleading pretenses. The undercover police officer who is invited into the suspect’s business is not committing a Fourth Amendment violation. The suspect assumed the risk that his guest was not to be trusted. But that’s not how consent works in tort law: the undercover investigator who obtains entry to a business’s premises by lying about his purposes sometimes is a trespasser, as in Food Lion v. Capital Cities.

And finally, there is the question of what consequences are required to make an intrusion or misuse actionable at law. This is the source of the most famous distinction between trespass to land and trespass to chattels. The former, given the heightened protection afforded real property, will support a lawsuit for nominal damages. But the modern rule is that a suit for trespass to chattels will not lie unless the owner is dispossessed or deprived of the use of the chattel, its condition or value is impaired, or some other physical harm results.

Of course, none of these was the case in Jones: the car itself was materially unaffected. Thus, for Fourth Amendment purposes, it appears that that the harm rule does not apply to trespass to chattels. A “technical trespass” causing no damage will not give rise to a tort suit, but it will trigger the Fourth Amendment. As Justice Alito notes, “Attaching such an object is generally regarded as so trivial that it does not provide a basis for recovery under modern tort law.” To be precise, the Second Restatements of Torts describes such intrusions as trespasses to chattels, but does not make them actionable at law.

Seizure law tracks tort law here: there must be “some meaningful interference” with the right to possession. But search law does not. As Jones explains, a trespassory search is a technical trespass plus “an attempt to find something or to obtain information.” So here, the Fourth Amendment is now more zealously protective than tort law is.

And this loops us back to the central theme of Jones, one that runs through all of these issues: the relationship between property, tort, and privacy. For trespass to land, the dignitary interest in privacy is one of the most commonly invoked reasons for protecting against intrusion even when there are no tangible harms. In the language of the 1814 English case Merest v. Harvey:

Suppose a gentleman has a paved walk in his paddock, before his window, and that a man intrudes and walks up and down before the window of his house, and looks in while the owner is at dinner, is the trespasser permitted to say “here is a halfpenny for you which is the full extent of the mischief I have done.” Would that be a compensation? I cannot say that it would be… .”

Thus, privacy values become a core justification for the right to exclude—even in cases where privacy itself is not at stake. Jones turns this theory back: the right to exclude becomes the measure of when society will protect privacy interests. Whether this is exactly right or exactly backwards, the reader is invited to consider.