Reading the Privacy & Civil Liberties Oversight Board’s rather tepid report on NSA surveillance under §702 of the FISA Amendments Act last night, I found myself thinking of the Supreme Court’s recent Riley opinion rejecting facile analogies between smartphones and other small personal objects subject to search—in particular Justice Roberts’ striking assertion that a search of a modern cell phone would expose to the government more private and intimate information than “the most exhaustive search of a home.”

It’s something of a cliché at this point that jurisprudence applying the Fourth Amendment to new technologies often hinges critically on the choice of metaphors to more ordinary physical searches, none of which ever quite capture all the salient differences between the digital and analog worlds. The one I’m about to offer is no exception, but I do want to explore how the choice of one (admittedly inadequate) frame over another affects our intuitions about surveillance. I also hope it may highlight some some assumptions embedded in our ordinary way of talking about electronic spying, which typically takes a wiretap of a one-to-one conversation on a personal telephone line as the basic template for all surveillance, obscuring the enormous variety of ways we use the Internet to interact.

Imagine a place I’ll call Cloud City. No, not Lando Calrissian’s floating metropolis, but a sprawling complex of buildings located near a major American airport. Catering primarily to frequent travelers, both American and foreign, Cloud City encompasses a wide variety of different facilities and services. There are condos and rented apartments and hotel rooms for individuals, but also suites designed for small groups of occupants, as well as larger meeting rooms and conference spaces that can be used for both public and private events of all sizes.

Each of these many different types of rooms and facilities may be rented or purchased by an American or a foreigner, by an individual human being or by some association or corporation. Sometimes the “person” who rents a room will be the only occupant, but often that won’t be the case at all. Many travelers will stay in rooms booked on the corporate credit card, visit another guest for a romantic tryst, or gather in suites and meeting rooms for conventions, business dealings, artistic collaboration, or just casual conversation. Some rooms will be open to anyone strolling by, some suites will encompass both public areas and locked bedrooms, and others will be entirely private. In principle, Cloud City’s cleaning and maintenance staff will often have access to even the private rooms for limited purposes, though dumbwaiters and Roombas allow most routine services to be automated.

For convenience, every building, floor, and room in Cloud City has a numerical address, which the inhabitants call “selectors,” because they can be entered on the control panel of the Great Glass Elevators, borrowed from Willy Wonka, to select and travel to different destinations in the city.

As we might expect with any sizable population, some of the visitors and residents of Cloud City are criminals, and a few are even spies or terrorists. Some of them may even be engaged in criminal activity right in their rooms—or talking about misdeeds they’ve committed in the past. But of course, the vast majority, both American and foreign, are normally law-abiding folks.

Now suppose a law is passed authorizing extremely broad court orders. Under one of these sweeping orders, government agents can activate cleverly concealed cameras and microphones in any room that is rented under the name of a foreigner, or even an American’s room if the Wonkavator logs show there’s probably at least one foreign visitor present. The agents are supposed to have a foreign intelligence reason to search a room, but nobody much asks just what the reason is before the cameras come on, and they can bring the regular police along in case they happen upon someone smoking a joint in the bathroom. In fact, once a room has already been searched, the police can go back and use the “selector” for an American’s apartment to review the tapes from the rooms they’ve visited to see what they got up to with their foreign friends. When, as often happens, the government agents happen upon Americans engaged in legal private activity, they’re supposed to forget what they’ve seen.

What would our courts have to say about this new law and these broad court orders? If it were on a law school test, you’d think it was a trick question: These orders are obviously unconstitutional general warrants. Would it matter that these searches often yield useful information? Surely not: Nobody thinks we prohibit general warrants because they never turn up genuine evidence. What about the objection that government agents (at least initially) only search rooms with “selectors” they’ve linked to a foreigner one way or another? Surely that, too, would be beside the point: What matters, we’d intuitively say, is that the government is spying on Americans in private spaces on American soil, not what particular sequence of buttons was used to turn the cameras on, or what motives led to the decision to activate them. Nor would we necessarily be impressed if research showed that the government was usually correct about the presence of a foreign visitor.

Like all metaphors for electronic surveillance, this one is imperfect in various ways. Most obviously, a foreign visitor would fall under the protection of the Fourth Amendment by dint of being physically present, in a way foreigners merely communicating by means of U.S. facilities do not. Nor does this description capture very well what happens when NSA engages in “upstream” collection, scanning vast quantities of international traffic in order to filter out and capture specific communications.

But Cloud City is still, I think, a helpful intuition pump. It highlights, for one, how irrelevant the issue of “targeting” would normally be to the question of whether a search presumptively requiring a specific, probable cause warrant has occurred. Private “spaces” on American soil do not lose their private status or their Fourth Amendment protection just because one person present in them may not be a member of “the people” referred to in the text of the Amendment. There may be cases where “special needs” justify warrantless searches of those spaces, but these should be narrow and relatively rare.

It also, I think, captures something important about the range of ways we use modern communications that is too easily elided when our baseline metaphor is the person-to-person telephone call. There is a reason “cyberspace” quickly became a common way of talking about the Internet, while “phonespace” or “mailspace” mostly just sound silly.

An individual e-mail or IM chat, to be sure, may not be relevantly much different from a phone call or a letter. Increasingly, though, we interact on platforms that feel much more “place-like”: They persist as shared environments for interaction beyond particular, ephemeral communicative acts. Think of a shared Facebook page or Google Group that over time accumulates digital furniture in the form of shared photos, videos, and text notes. That these “spaces” may be shared—perhaps even with people who live abroad—rather than the exclusive province of a single individual does not mean we think of them as any less private, at least when relatively few people hold a key. As the cloud evolves, it seems clear that more and more data we naturally think of as private is going to reside partly in such shared spaces.

In the physical world, we struck a constitutional deal that grants government agents access to private spaces only pursuant to a specific warrant or under narrowly defined, exceptional circumstances. In Cloud City, the government has already altered the deal—let’s pray they do not alter it any further.