How did Yates v. United States limit enforcement of the Smith Act?

In Yates v. United States (1957), the U.S. Supreme Court significantly limited the enforcement of the Smith Act by narrowing the legal definition of prohibited speech.12

While the court had previously upheld the act's constitutionality in Dennis v. United States (1951)—allowing the government to restrict speech that posed a potential threat to national security—Yates adopted a much stricter interpretation of the law's advocacy provision. The court ruled that "advocacy" under the Smith Act must be construed to mean only speech that includes the actual incitement to unlawful action.12

By distinguishing between the abstract teaching of revolutionary doctrine and the active incitement to commit specific violent acts, the ruling effectively raised the evidentiary burden for the government. Consequently, while the Smith Act remained on the books, this decision rendered parts of it unenforceable and halted further prosecutions under the statute.12