In United States v. Carpenter, 585 U.S. ---, No. 16-402 (2018), the Supreme Court limited the third-party doctrine, and held that the government must typically get a warrant to obtain cell-cite location information.
As framed by the Chief Justice, the issue was "whether the Government conducts a search under the Fourth Amendment when it accesses historical cell phone records that provide a comprehensive chronicle of the user’s past movements."
In holding that it does conduct a search under those circumstances, the Court considered a person’s expectation of privacy in his physical location and movements, as well as the third-party doctrine, under which the Government is typically free to obtain information from the third-party recipient without triggering Fourth Amendment protections.
The Court held: "Given the unique nature of cell phone location records, the fact that the information is held by a third party does not by itself overcome the user’s claim to Fourth Amendment protection. Whether the Government employs its own surveillance technology as in Jones or leverages the technology of a wireless carrier, we hold that an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI [cell-site location information]."
Although the Court was careful to craft a narrow ruling, this case has broad implications for other digital data held by third parties, like Google. On this point, I suggest also reading Justice Gorsuch's dissent, which is less an actual dissent and more of a call toward broader protection of digital data.
