Seattle-based Prison Legal News filed the lawsuit in U.S. District Court on Wednesday against the Nashville, Tenn. company and various officials at the Saguaro Correctional Center in Eloy, Ariz., halfway between Phoenix and Tucson.

Prison Legal News, which also publishes, sells, and distributes books to about 7,000 prisoners around the world, accuses prison officials of prohibiting at least six Saguaro prisoners from receiving books in the last two years.

Calls to Saguaro warden Todd Thomas and Corrections Corporation of America were not immediately returned Wednesday.