Question

Why were the Japanese-American Internment camps a violation to the constitution?

Answer 1

They violated a number of basic rights under the Constitution such as "equal protection under the law". They were simply ordered off their land and then placed in relocation camps violating most of the rights put into place by the law to protect American citizens.

Here's a good breakdown of all of the rights violated by the internment of Japanese Americans in WW2:
http://bss.sfsu.edu/internment/rightsviolated.html

And a nice writeup on the event on PBS:
http://www.pbs.org/thewar/at_home_civil_rights_japanese_american.htm

Answer 2

Arguably because of the equal protection clause of the 14th Amendment, and the due process clause of the 5th. Citizens were imprisoned without being convicted of a crime, and due just to their perceived proclivity towards a crime (in this case treason), and simply because they belonged to a class of people (Japanese ancestry) and not through any assessment of the individual.

This is all on pretty weak ground, however, because it was a wartime temporary measure, and both the Constitution and common law give the President extremely broad powers in wartime. For example, it is often said that the US President is not "above the law." However, when he is acting as Commander in Chief, he is, in fact, above the law, because he is exercising powers given to him directly by Article II of the Constitution, and the Supremacy Clause (which says the Constitution supersedes any law) mean he cannot be constrained by any act of Congress (i.e. a law) or judicial ruling. He can, in essence, rule directly by decree -- but only so long as he is acting as Commander in Chief, the nation's wartime leader.

The tricky bit, therefore, is just how far the Presidents authory as Commander in Chief goes. Certainly he can order the armed forces of the United States into action, and command any aspect of their activities. (For example, were Congress to pass a law requiring the President to send troops to or remove them from Afghanistan, the President is entitled to ignore it. Similarly, if a Federal court puts a restraining order on a soldier and orders him not to fire his weapon while in uniform, the President can ignore that.)

And it's generally acknowledged that the President must have *some* degree of command over things not directly connected with military operations to successfully prosecute a war. For example, he ought to be able to commandeer transportation (boats, airplanes, trucks) if necessary, or close ports, restrict international trade, require certain kinds of secrecy with respect to military or military-related information.

But on the other hand, very few people believe the President can do absolutely anything he wants in wartime. So the issue of what, exactly, the President can do with his Article II Command in Chief powers is still strongly debated. As a rule, in the United States, rulings by the Supreme Court are usually taken to establish what is, and is not, consistent with the Constitution. The case of the Japanese-American internment was appealed to the Supreme Court in the case of Korematsu v. the United States, in 1944, and the Supreme Court ruled that the internment was constitutional. Since that decision has not yet been overturned, the internment is, at this time, still considered constitutional.