evil that rises far above public inconvenience, annoyance, or unrest. Justice William O. Douglas wrote for the Court that "a function of free speech under our system is to invite dispute. It may indeed best serve its high purpose when it induces a condition of unrest, creates dissatisfaction with conditions as they are, or even stirs people to anger." Although the Court referred to the clear and present danger test in a few decisions following Thornhill, the bad tendency test was not explicitly overruled, and the clear and present danger test was not applied in several subsequent free speech cases involving incitement to violence. In 1940, Congress enacted the Smith Act, making it illegal to advocate "the propriety of overthrowing or destroying any government in the United States by force and violence". The statute provided law enforcement a tool to combat Communist leaders. Eugene Dennis was convicted in the Foley Square trial for attempting to organize a Communist Party. In Dennis v. United States (1951), the Court upheld the Smith Act. Chief Justice Fred M. Vinson relied on Holmes' "clear and present danger" test as adapted by Learned Hand: "In each case [courts] must ask whether the gravity of the 'evil', discounted by its improbability, justifies such invasion of free speech as necessary to avoid the danger." Clearly, Vinson suggested, clear and present danger did not intimate "that before the Government may act, it must wait until the putsch is about to be executed, the plans have been laid and the signal is awaited." In a concurring opinion, Justice Felix Frankfurter proposed a "balancing test", which soon supplanted the "clear and present danger" test: The demands of free speech in a democratic society as well as the interest in national security are better served by candid and informed weighing of the competing interests, within the confines of the judicial process. In Yates v. United States (1957), the Supreme Court limited the Smith Act prosecutions to "advocacy of action" rather than "advocacy in the realm of ideas". Advocacy of abstract doctrine remained protected while speech explicitly inciting the forcible overthrow of the government was punishable under the Smith Act. During the Vietnam War, the Court's position on public criticism of the government changed drastically. Though the Court upheld a law prohibiting the forgery, mutilation, or destruction of draft cards in United States v. O'Brien (1968), fearing that burning draft cards would