MITCHELL v. HARMONY, 54 U.S. 115 (1851) But we are clearly of opinion, that in all of these cases the danger must be immediate and impending; or the necessity urgent for the public service, such as will not admit of delay, and where the action of the civil authority would be too late in providing the means which the occasion calls for. It is impossible to define the particular circumstances of danger or necessity in which this power may be lawfully exercised. Every case must depend on its own circumstances. It is the emergency that gives the right, and the emergency must be shown to exist before the taking can be justified. [54 U.S. 115, 135] In deciding upon this necessity, however, the state of the facts, as they appeared to the officer at the time he acted, must govern the decision; for he must necessarily act upon the information of others as well as his own observation. And if, with such information as he had a right to rely upon, there is reasonable ground for believing that the peril is immediate and menacing, or the necessity urgent, he is justified in acting upon it; and the discovery afterwards that it was false or erroneous, will not make him a trespasser. But it is not sufficient to show that he exercised an honest judgment, and took the property to promote the public service; he must show by proof the nature and character of the emergency, such as he had reasonable grounds to believe it to be, and it is then for a jury to say, whether it was so pressing as not to admit of delay; and the occasion such, according to the information upon which he acted, that private rights must for the time give way to the common and public good.

Prejudice against immigrants from Asia had been longstanding on the West Coast when World War II broke out following the Japanese attack on Pearl Harbor. Within a few weeks the demand spread that Japanese Americans, both naturalized citizens as well as those born in the United States, any of whom might be "saboteurs" or "spies," be removed from the West Coast before the Japanese invaded. The fact that no proof existed that a single one of these people constituted a threat to the United States made no difference. Even the respected columnist Walter Lippmann informed his readers that "nobody's constitutional rights include the right to reside and do business on a battlefield. There is plenty of room elsewhere for him to exercise his rights." On February 19, 1942, President Roosevelt signed Executive Order 9066 authorizing the Secretary of War to designate parts of the country as "military areas" from which any and all persons might be excluded, and in which travel restrictions might be imposed. A few weeks later General John L. DeWitt, in charge of the Western Defense Command, designated the entire Pacific coast as a military area because of its susceptibility to attack. Curfews were established, and Japanese Americans were at first prohibited from leaving the area, and then from being in the area. The only way Japanese Americans could comply with these contradictory orders was to submit to evacuation to relocation centers in the interior.