Only the film's copyright holder can release it into the public domain. They must do so by an overt act or statement that indicates the work is no longer subjec

Only the film's copyright holder can release it into the public domain. They must do so by an overt act or statement that indicates the work is no longer subject to copyright. Merely submitting copies of the work to a court as part of a lawsuit doesn't do this as there is no statement that copyright is relinquished. Quite the opposite--copies of the film still bear a copyright notice.