His case was eventually reviewed by the Supreme Court, which decided that the burden of proof must be on the government to prove that Nishikawa's Japanese military service was undertaken voluntarily before he could be stripped of his citizenship.

He testified that in addition to the legal penalties for draft evasion, he was afraid of the violent reputation of the Japanese secret police and had been told that the US consulate would not have assisted him if he had sought help to avoid conscription.

After Pearl Harbor, when he said to other Japanese soldiers that Japan could not win the war, he was regularly beaten every day for a month.

In Schneiderman v. United States, 320 U.S. 118, the court had held that in a case concerning "the precious right of citizenship ... we believe the facts and the law should be construed as far as is reasonably possible in favor of the citizen."

Chief Justice Warren delivered the opinion of the court: Because the consequences of denationalization are so drastic petitioner's contention as to burden of proof of voluntariness should be sustained ...

The fact that this petitioner, after being conscripted, was ordered into active service in wartime on the side of a former enemy of this country must not be permitted to divert our attention from the necessity of maintaining a strict standard of proof in all expatriation cases.