The United States government is attempting to force Facebook to break the encryption in its Messenger app, Reuters has reported.
Facebook is fight the Department of Justice’s demand in court, and details of the case have not yet been made public.
Prosecutors are seeking a wire tap of phone conversations over Messenger for one particular user.
Messages sent over Messenger use end-to-end encryption, meaning they can only be be viewed by the sender and recipient.
Facebook is arguing that it will only be able to comply with the request if it rewrites all the code that users rely upon.
The case echoes the 2016 fight between the FBI and Apple, when the former wanted access to an iPhone that belonged to a dead mass shooting culprit.
