In its early years, Wolf Popper litigated constitutional rights in highly publicized trials. The McCarthy era and the Red Scare of the 1940 's engendered the prosecution of many important people in the movie industry, who were subpoenaed to appear before the House Un-American Activities Committee on suspicion of holding communist loyalties. Pursuing a goal of strengthening the American system, Wolf Popper played a key role in defending the First Amendment rights of the so called “Hollywood Ten,” counting among them some of the best film industry talent of the time. The Firm also represented, in various legal matters, many of those artists, among them Paul Robeson, Ring Lardner Jr., Dalton Trumbo and Albert Maltz.