President Franklin D. Roosevelt authorized Executive Order 9066, issued two months after Pearl Harbor. The order allowed regional military commanders to designate "military areas" from which "any or all persons may be excluded. Although the executive order did not mention Japanese Americans, this authority was used to declare that all people of Japanese ancestry were required to leave Alaska, and the military exclusion zones from all of California and parts of Oregon, Washington, and Arizona, except for inmates who were being held in government camps.
Source: Britannica Academic