The issues of prior restraint and press censorship are examined in this paper, which focuses on the 1970 Williams v. O'Brien court case. The paper discusses the litigation, in which Robert F. Williams, as an American citizen living in Peking, China, sued the United States Postmaster General over the banning of the May 1967 issue of "The Crusader," a periodical he published and distributed to the United States and other countries from Peking. (The Postmaster General had banned the issue citing an act of congress that provides for the nonmailability of matter tending to incite arson, murder, or assassination, and other national security related provisions of the United States.) The first section of the paper traces the history of postal censorship in this country from the Washington administration forward, and then presents a detailed exposition of the plaintiff's arguments--that the breadth and vagueness of the censorship statutes put them in violation of First and Fifth Amendment freedoms, and that no notice or judicial hearing to determine mailability was provided for in these statutes. The defendant's answer follows, leading into an explanation of the decision rendered by a three-judge panel of the U. S. District Court for the District of Columbia. A concluding section discusses the parallels between this case and the subsequent Pentagon Papers case (New York Times v. United States), and raises the question of whether "The Crusader" and its publisher were victims of a de facto bill of attainder. (RBW)