It was de facto banned from 1919 to 1921 after a series of unattributed bombings, and attempted assassinations of both government officials and judges that were later traced to militant adherents of the radical anarchist Luigi Galleani. Many then recent immigrants ere also needlessly jailed or expelled as a result of this to. It was witch-hunted by the House Committee on Un-American Activities from 1947 to 1958, after it actively undermined American frorigen policy in World War 2.