The Court held that government entities violate the Fourth Amendment to the United States Constitution when accessing historical CSLI records containing the physical locations of cellphones without a search warrant.

[1] Prior to Carpenter, government entities could obtain cellphone location records from service providers by claiming the information was required as part of an investigation, without a warrant, but the ruling changed this procedure.

[4] Service providers capture and store this data for business purposes, such as troubleshooting, maximizing network efficiencies, and determining whether to charge customers roaming fees for particular calls.

As technology advanced in the 2010s, the Supreme Court began to modify its precedents on government searches of personal communications devices, given new consumer behaviors that may transcend the third-party doctrine.

[10] Between December 2010 and March 2011, several individuals in the Detroit, Michigan area conspired and participated in armed robberies at RadioShack and T-Mobile stores across the region.

[15] This ruling was largely based on the Smith v. Maryland precedent, stating that Carpenter used cellular telephone networks voluntarily, and per the third-party doctrine he had no reasonable expectation that the data should be private.

[1] In United States v. Jones (2012) the Court had ruled that GPS tracking could constitute a search under the Fourth Amendment as a violation of a person's reasonable expectation of privacy.

Ultimately, in Carpenter the court determined that the third-party doctrine could not be extended to historical cell site location information (CSLI).

Instead, the Court compared "detailed, encyclopedic, and effortlessly compiled" CSLI records to the GPS information at issue in United States v. Jones, recognizing that both forms of data accord the government the ability to track individuals' past movements.

[24] Furthermore, the Court noted that CSLI could pose even greater privacy risks than GPS data, as the prevalence of cellphones could accord the government "near perfect surveillance" of an individual's movements.

Accordingly, the Court ruled that, under the Fourth Amendment, the government must obtain a search warrant in order to access historical CSLI records.

At the same time, this tool risks Government encroachment of the sort the Framers [of the U.S. Constitution], after consulting the lessons of history, drafted the Fourth Amendment to prevent.

"[30] Gorsuch further recommended that the third-party doctrine, as well as Katz v. United States, be overturned as inconsistent with the original meaning and application of the Fourth Amendment.

"[34] Thomas goes on further to write that, "The Fourth Amendment, as relevant here, protects '[t]he right of people to be secure in their persons, houses, papers, and effects, against unreasonable searches.'

However, the Circuit Court judges concluded that the FBI was acting in good faith with respect to collecting the data based on the law at the time the crimes were committed.

[36] The Supreme Court's ruling in Carpenter was narrow and did not otherwise change the third-party doctrine related to other business records that might incidentally reveal location information, nor did it overrule prior decisions concerning conventional surveillance techniques and tools such as security cameras.

The Court did not extend its ruling to other matters related to cellphones not presented in Carpenter, including real-time CSLI or "tower dumps" (the downloading of information about all the devices that were connected to a particular cell site during a particular interval).