In Executive Order 9066, Franklin Roosevelt granted sweeping powers to the Secretary of War in general, and to military commanders indirectly, to restrict the movement of Japanese-Americans. Acting "whenever they deem desirable," the order read, military commanders could "prescribe military areas" where
the right of any person to enter, remain in, or leave shall be subject to whatever restrictions the Secretary of War or the appropriate Military Commander may impose in his discretion.
What this meant in practice was that individuals whose loyalty was suspect, and who lived in areas deemed militarily vulnerable or sensitive, could be moved out of those areas. The Order also authorized commanders to provide "shelter" and other necessities for the people who were moved out of these areas. Under the circumstances, the entire West Coast was deemed vulnerable to Japanese attack, and numerous governors and anti-Japanese politicians, as well as some military leaders, had argued that in case of attack, people of Japanese ancestry in the area might serve the attackers as sabateurs and spies. So they were taken to internment camps, where they could be under the constant surveillance of armed guards. The power granted to the War Department to enforce this order was thus sweeping and extraordinary, only really paralleled by Indian removal policies in the nineteenth century.