America forcibly removed Japanese Americans following the attack on Pearl Harbor because there was a risk of Japanese spying. America had to ramp up production on almost everything during WWII, and in the event that there were Japanese spies, they could report all our weak and vulnerable points back to Japan. The Internment was, in my opinion, necessary. National security is not something the take lightly. If Japan knew all our vulnerabilities, they could have crippled us. The constitution, if I recall right, doesn't say anything about not being able to relocate a certain mass of people.
