I don't want any of them [persons of Japanese ancestry] here. They are a dangerous element. There is no way to determine their loyalty... It makes no difference whether he is an American citizen, he is still a Japanese. American citizenship does not necessarily determine loyalty... But we must worry about the Japanese all the time until he is wiped off the map.[47][48]
DeWitt also sought approval to conduct search and seizure operations which were aimed at preventing alien Japanese from making radio transmissions to Japanese ships.[49] The Justice Department declined, stating that there was no probable cause to support DeWitt's assertion, as the FBI concluded that there was no security threat.[49] On January 2, the Joint Immigration Committee of the California Legislature sent a manifesto to California newspapers which attacked "the ethnic Japanese," who it alleged were "totally unassimilable."[49] This manifesto further argued that all people of Japanese heritage were loyal subjects of the Emperor of Japan; the manifesto contended that Japanese language schools were bastions of racism which advanced doctrines of Japanese racial superiority.[49]
The manifesto was backed by the Native Sons and Daughters of the Golden West and the California Department of the American Legion, which in January demanded that all Japanese with dual citizenship be placed in concentration camps.[49] By February, Earl Warren, the Attorney General of California (and a future Chief Justice of the United States), had begun his efforts to persuade the federal government to remove all people of Japanese ethnicity from the West Coast.[49]