Dozens of rights groups and campaigners have signed a letter calling on Facebook to “drop all attempts to silence whistleblower Daniel Motaung”.
They accuse the tech giant of trying to “crush his efforts to improve labour conditions for Facebook moderators in Kenya and around the world”.
Mr Motaung says he was paid about $2.20 (£1.80) per hour by Sama, one of Facebook’s contractors, to review posts including beheadings and child abuse. He is suing both firms in a Kenyan court.
In response, both Sama and Facebook applied for a gag order on Mr Motaung, saying that he could prejudice the outcome of the case by talking to the media.
Facebook and its parent company Meta have not responded to the letter – which was signed by Facebook whistleblower Frances Haugen, author Shoshana Zuboff, and the Africa Freedom of Information Centre, among others.