The American Civil Liberties Union (ACLU) is suing two Homeland Security agencies, Customs and Border Protection (CBP) and Immigration and Customs Enforcement (ICE), for failing to turn over documents related to the use of cell site simulators, also known as 'stingrays'. The ACLU filed a Freedom of Information Act request in 2017 to learn more about the technology and how it's used. The agencies have failed to produce records, and the ACLU is now seeking a court order to compel them to turn over the documents. The use of stingrays has raised concerns about surveillance and privacy.