The assassination of President McKinley by Leon Czolgosz in September 1901 — a man with only glancing contact with the anarchist movement — triggered the first American statutes criminalizing a political doctrine by name. New York's 1902 criminal anarchy law made advocating the overthrow of government by force a felony, punishing speech itself; New Jersey, Wisconsin, and Washington followed. Anarchists were mobbed, meeting halls closed, and Johann Most was imprisoned yet again merely for republishing a decades-old article.
Congress joined in with the Immigration Act of 1903, the Anarchist Exclusion Act — the first federal law since 1798 to bar immigrants for their beliefs. Its test case was John Turner, a mild English trade-union organizer arrested at a New York lecture in October 1903 and held at Ellis Island for deportation. The Free Speech League fought the case to the Supreme Court, which upheld the statute in 1904, establishing that noncitizens could be expelled for ideology alone — the legal foundation on which the Palmer raids, the Buford deportations, and every subsequent ideological-deportation campaign would be built.