When President William McKinley was assassinated in 1901 by an American anarchist with a foreign-sounding name , a new wave of xenophobia was unleashed . Calls to exclude anarchists from immigrating intensified , and Theodore Roosevelt 's first Congressional address urged the exclusion of aliens who even espoused anarchist beliefs . At least nine anti-anarchist bills were introduced in the first session of the 57th Congress , and several Constitutional amendments were proposed that would have permitted the suppression of anarchism . The effort came to fruition in the Immigration Act of 1903 , the first act barring immigration solely on the basis of political belief
assassinated
Assassination of William McKinley
Ideological restrictions on naturalization in U.S. law