EO 9066 was the internment order for Japanese Americans (as well as some Germans and Italians), most of whom were US citizens.
The Contert of the Decision. First, the exclusion and removal
were attacks on the ethnic Japanese which followed a long and ugly
history of west coast anti-Japanese agitation and legislation. Antipathy
and hostility toward the ethnic Japanese was a major factor of the public
life of the west coast states for more than forty years before pearl
Harbor. under pressure from california, immigration from Japan had
been severely restricted in 1908 and entirely prohibited in 1924. Japanese immigrants were barred from American citizenship, although
their children born here were citizens by birth. california and the
other western states prohibited Japanese immigrants from owning land.
In part the hostility was economic, emerging in various white American
groups who began to feel competition, particularly in agriculture, the
principal occupation of the immigrants. The anti-Japanese agitation
also fed on racial stereotypes and fears: the "yellowperil" of an unknown
Asian culture achieving substantial influence on the Facific coast or of
a Japanese population alleged to be growing far faster than the white
population' This agitation and hostility persisted, even though the
ethnic Japanese never exceeded three percent of the population of
California, the state of greatest concentration.
https://www.archives.gov/files/research/japanese-americans/justice-denied/summary.pdf
