Other lawmakers are alarmed by the FBI’s disclosure of having purchased location information derived from people’s cell phones. During a hearing in March, the FBI director, Christopher Wray, told senators that the bureau had “previously—as in the past—purchased some such information for a specific national security pilot project.”

Americans have a reasonable expectation of privacy, the US Supreme Court says, when it comes to certain digital information, including that which could reveal “the whole of their physical movements.” Such data—which the court describes as “detailed, encyclopedic, and effortlessly compiled”—need not be GPS-precise merely to justify a warrant. Nevertheless, the government has widely adopted the view that the Fourth Amendment does not apply when that same data is available to it commercially. 

When provided, the government’s reasoning typically hinges on analysis of the landmark 2018 Carpenter v. United States decision, in which the Supreme Court ruled that the government’s warrantless acquisition of cellular records, which can be used to track a person’s movements, had violated the rights of a 32-year-old man who’d been convicted of carrying out a string of robberies.

In its 5–4 opinion, the court refers to police demanding or “compelling” access to data, something that literal interpreters of the law say places commercial arrangements with data brokers squarely outside the scope of the court opinion. What’s more, government lawyers have pointed to acknowledgment from the court that the debate over Carpenter did not consider “collection techniques involving foreign affairs or national security.”

The Supreme Court has erstwhile framed the Fourth Amendment as a means to “plac[ing] obstacles in the way of a too permeating police surveillance,” something that the Constitution’s authors deemed a “greater danger to a free people than the escape of some criminals from punishment.” Oft-cited by the court is a passage by a 19th-century American jurist: “Of all the rights of the citizen, few are of greater importance or more essential to his peace and happiness than the right of personal security, and that involves not merely protection of his person from assault, but exemption of his private affairs, books, and papers, from the inspection and scrutiny of others. Without the enjoyment of this right, all others would lose half their value.”

What rules or guidelines do exist within the intelligence community for purchasing commercial data often justify the activity by deeming the information “publicly available,” pointing to the fact that it may be open for purchase by not only private companies but foreign governments as well. While true and worrying, that is also irrelevant, says Bob Goodlatte, the former chairman of the House Judiciary Committee who now works as a senior policy adviser for the Project for Privacy & Surveillance Accountability, a pro-privacy group.

“None of those other entities can arrest you, can charge you with a crime, try you, sentence you, imprison you, restrain you, enjoin you, fine you, tax you,” Goodlatte says. “All of those are powers of government, and any American should be concerned about the ease with which the federal government can gather information about people.”