More background on the letter and who has signed it in this AP wire story running on CBC, among others.

A coalition of advocacy groups organized the letter, including the Committee for the First Amendment — a free speech group led by Jane Fonda — as well as the Democracy Defenders Fund and the Future Film Coalition. Other signatories include: Ben Stiller, Don Cheadle, Javier Bardem, Lily Gladstone, Lin-Manuel Miranda, Tiffany Haddish and Ted Danson.