Oh, that's right. There weren't any! The American government had some unique challenges in maximizing their chances of winning the war against a zealous and absolutely ruthless enemy (Japan). It would have been extremely irresponsible not to at least attempt to neutralize the threat posed by the population of first-generation citizens.
American authorities acted within their rights in making a reasonable effort to neutralize domestic saboteurs or collaborators by interning these people. Of course it's sad that it happened, but remember that battles such as Midway were won through superior intelligence and code-breaking. A single Japanese acting as a spy might have overturned that. It would have been very bad for east Asia had Japan won. They were committing numerous, documented war crimes and would have continued to do so.