The American Civil Liberties Union today released documents related to a secret subpoena and gag order sent to one of the country’s main providers of encryption technology and communications services. The company, Open Whisper Systems, complied with the subpoena, turning over the limited customer information it had — but the gag order was lifted after the ACLU formally protested it as a violation of the company’s free speech rights.

Open Whisper makes the encrypted-communications app Signal, which allows users to have secure phone calls and text message conversations. The company is also behind the Signal Protocol, which powers the encryption built into Facebook Messenger, Google’s Allo, and WhatsApp.