Because of the misguided belief that Japanese people had some sort of divine loyalty to their emperor, regardless of what country they lived in or were citizens of, the main (and completely unfounded) worry was that Americans of Japanese descent would sabotage and destroy US military infrastructure to aid Japan in the war. Since the 1800s, Chinese immigrants to California have caused issues of many kinds. There was a strong desire to intern the Japanese as "enemy combatants" as a result of a combination of anti-Japanese hysteria in California, led by Governor Earl Warren (the same Warren, incidentally, who was responsible for the landmark civil rights cases Brown v. Board of Education, Gideon v. Wainwright, and Miranda v. Sims). This, however, only extended to Japanese people living in the US's mainland. The fact that the Japanese were a relatively small minority in the continental US made it possible for this to be accomplished since any disturbance caused by their imprisonment would have been minimal (indeed many people essentially "stole" property of Japanese Americans, or purchased it for pennies on the dollar). On the other hand, Hawaii's sizable Japanese population made up more than 30% of the island. The war effort would be harmed by imprisoning them, especially while Pearl Harbor was running at full capacity. This was part of the reason why the Japanese American volunteers came primarily from Hawaii-they had less restrictions on them than internees, and they also were not as resentful against the US government as a result.