Last week, I wrote a post on the Playpen warrant currently being litigated in federal courts around the country. My post included a section, “Retrieving IP Addresses is Clearly a Search,” that said the following:

A significant amount of media attention about the Playpen cases has focused on a curious argument. A minority of the judges have held that the the Playpen searches were constitutional because they weren’t searches at all. According to this argument, a person has no Fourth Amendment rights in IP addresses. Because the most important information obtained by the NIT was IP addresses, use of the NIT was not a search and no Fourth Amendment rights were violated. As far as I can tell, the government has not actually made this argument. Rather, it is a position introduced by one judge and then adopted by some others.
This argument is clearly wrong, though. Individuals have Fourth Amendment rights in information stored inside their computers unless they voluntarily share the information. A person using Tor has not voluntarily shared his IP address with the websites he visits. Indeed, the absence of voluntarily sharing is precisely what led the government to surreptitiously obtain the information using the NIT. Given that a Tor user has not voluntarily shared his IP address, it doesn’t matter that obtaining an IP address from a third party or a visited website would not be a search in other circumstances that did involve voluntarily sharing.
Put another way, it’s the way of obtaining information that makes the act a search, not the information itself in the abstract. This point is obvious in the physical world. See Arizona v. Hicks, 480 U.S. 321 , 325 (1987) (“A search is a search, even if it happens to disclose nothing but the bottom of a turntable.”). It should be equally obvious with computers. If the police want to read today’s newspaper, they can’t break into my house and open my desk drawer to find my copy without committing a search. The fact that they could have read the newspaper by finding a copy in public doesn’t mean they can break into my house to read mine. Similarly, the fact that IP addresses may be available without searching a target in some cases doesn’t mean they can break into his computer to find the IP address without committing a search.

Here’s a follow-up.

First, several readers pointed out that the government actually has made this argument. You can read the government’s argument here in the Michaud case (pages 6-7) and here in the Lemus case (pages 8-12). My apologies for the misstatement, and thanks to reader Jonathan Mayer for sending on the briefs.

Second, some readers argued that a Tor user loses a reasonable expectation of privacy in IP addresses because the user must disclose his true IP address to Tor. This is essentially the argument the government (briefly) makes in Michaud: By using Tor, you are sending your IP address to Tor, which is ultimately hosted by “an unknowable collection of strangers” who are running Tor exit nodes. You have put out your IP address to lots of people, which means that you have no expectation of privacy in it.

That argument doesn’t work. Fourth Amendment law regulates how the government learns information, not what information it learns. Where the government gets the information controls what is a search. If the government wants to obtain public information that I have stored in a private place, such as in my house, it’s a search for the government to enter that private place. Conversely, if the government wants to obtain private information that I have put in a public place, it’s not a search for the government to go to the public place and observe it. It’s the place that matters, not the abstract status of the information. Government access to information stored inside a suspect’s computer without permission is a search regardless of whether the information has been voluntarily revealed in some other way to someone else.

A physical world analogy might make the point more intuitive. Imagine I want to invite lots of people to my birthday party. I mail out 300 paper invitations, and I have 20 invitations left over that I keep in my kitchen drawer. The police are investigating me for drug offenses, and they hear through the grapevine that the invitation says that there will be lots of cocaine at the party. The police want to get a copy of the invitation so they can get a warrant to search the place where the party will be held.

Whether the government conducts a search of my house, papers or effects when they obtain a copy of the invitation depends entirely on which copy of the invitation they obtain. On one hand, if the police obtain one of the invitations that I mailed out and that has already been delivered, then obtaining the invitation is not a search. Upon delivery of a letter, my Fourth Amendment rights as a sender extinguish. The police are free to seize as many copies of already-delivered letters as they want and it won’t implicate my Fourth Amendment rights.

On the other hand, the fact that there are hundreds of invitations circulating doesn’t mean that the police can break into my house and search my kitchen drawer to find the 20 invitations I never sent. Breaking into my house and opening my kitchen drawer is a search, no matter whether the information found inside there is something that I have disclosed elsewhere. If the government tried to argue that no search occurred when they broke into my house and rifled through my kitchen, because, well, they could have obtained the invitation some other way that is not a search, no judge would be convinced.

The same principle applies to computer searches, and that makes this an easy issue. What matters is how the government obtained the information, not whether it could have obtained the information some other way that would not be a search. If the police think they can obtain the information another way that isn’t a search, they are free to try. But if the police fail in their efforts, and the only way they can get the information is by accessing a Fourth-Amendment-protected space, then accessing that space is a search.