According to The fourteenth Amendment of the Constitution of the Unites States, the amendment states that the United States or any states are not allowed to take away or deprive anyone of life, liberty, or property without a legal procedure. With this said when the executive order 9066 was signed many people were deprived of liberty and property. It was seen as wrong of the President.
U.S Army General's report on the defense of the West Coast gave reasons why the Japanese were a possible threat. They thought that the Japanese on the coast could easily fight for Japan instead of the US because it is in their blood. Regardless of where they were born they would do what their parents would have wanted. In the document the General said the reason they would turn against the US is because they couldn't fully integrate into American society.
I believe that internment camps weren't the best idea because a lot of the population pushed into the camps were probably actually going to be loyal to the US. If a person wasn't to be loyal then those people could have been taken care of but also it wasn't known who was and who wasn't going to be loyal. They did what they had to do because we couldn't afford to lose.