The correct answer is: because it was issued under special circumstances during wartime.
Korematsu v. United States ( 1944 ) was a landmark Supreme Court decision concerning the execution of Executive Order 9066. This order ordered Japanese Americans into interment camps due to suspicions of espionage and their engagement against the United States.
The Court ruled that the need to protect the country against espionage outweighed the rights of Americans of Japanese descent, such as Fred Korematsu.
According to the Justices, Korematsu was not excluded from the Military Area because of his race but because the United States was at was with the Japanese Empire and the order was a way to protect America.