The SEC's Consolidated Audit Trail collects information on virtually every stock-market transaction in the United States, creating an enormous database that regulators can search for suspicious activity without first identifying a particular person or crime.

NCLA has long argued that this mass collection and searching of Americans' financial information violates the Fourth Amendment. Now, a new Supreme Court decision could strengthen that challenge.

On this episode of Unwritten Law, NCLA President and Chief Legal Officer Mark Chenoweth and Senior Litigation Counsel John Vecchione are joined by Margot Cleveland to discuss the Supreme Court's recent decision in Chatrie v. United States and its implications for NCLA's CAT challenge, Davidson v. SEC.

In Chatrie, the Supreme Court held that the government's use of Google's location database to identify people near the scene of a crime constituted a Fourth Amendment search. Rather than beginning with a suspect supported by probable cause, investigators searched a large pool of people's location information and worked backward to identify a suspect.

Mark, John, and Margot explain why they see a powerful parallel with CAT. The government collects vast amounts of trading data, runs algorithms against it looking for suspicious transactions, and then identifies the individuals behind those trades. As they put it, the government is using the search itself to develop the probable cause that ordinarily should precede a search.

They also discuss the “third-party doctrine,” whether Americans surrender their privacy rights simply because financial information passes through a broker, and why constitutional protections must keep pace with the government's increasingly powerful surveillance technology.