Police are allowed to spy on your cell phone's location without a warrant
North Carolina appeals court ruled cops don't need a warrant for mobile phone GPS location:
The American Civil Liberties Union filed an amicus brief arguing that police need a warrant:
“The vast majority of courts to consider the issue have concluded that the (Stored Communications Act) does not permit the government to obtain this type of prospective cell phone location information, and that prospective location information may only be obtained pursuant to a warrant supported by probable cause,” according to the brief. “These courts have identified numerous grounds for denying applications for prospective information under the SCA, most notably that the plain language of the statute does not allow it for at least four different reasons.”
The appeals court, in a unanimous opinion, disagreed.
“The trial court properly denied Defendant’s motion to suppress the cell tower site location information obtained by law enforcement,” according to the opinion. “These stored historical records were provided by AT&T, a third party, pursuant to a valid court order. Defendant had no reasonable expectation of privacy in these third-party records. … The procurement of this information was not a ‘search,’ and did not require the issuance of a warrant based upon probable cause."

image credit: Nathan Wessler, ACLU