After returning to the United States, he was arrested and charged with treason for having abused American prisoners of war.

In August 1943, with the assistance of a family friend, Takeo Miki, Kawakita took a job as an interpreter at a mining and metal processing plant..

In 1944 and early in 1945, approximately 400 American POWs, many of whom were captured in Bataan in 1942 and had survived the subsequent death march, arrived in the camp.

The prisoners also performed other general labor in the mine area, including such duty as carrying logs to be used for construction and maintenance work.

[7] After the end of the war, Kawakita renewed his U.S. passport, explaining away his having registered as a Japanese national by claiming he had acted under duress.

[3]: 142 In October 1946, a former POW, William L. Bruce saw Kawakita in a Los Angeles department store and recognized him from the war.

Bruce reported this encounter to the FBI, and in June 1947, Kawakita was arrested and charged with 15 counts of treason arising from alleged abuse of American POWs.

In an interview shortly after the arrest, Bruce described his reaction to seeing Kawakita:"I was so dumbfounded, I just halted in my tracks and stared at him as he hurried by.

[3]: 145  The prosecution argued that Kawakita had known he was still a U.S. citizen and still owed allegiance to the country of his birth—citing the statements he had made to consular officials when applying for a new passport as evidence that he had never intended to give up his U.S.

I want to make it perfectly clear that the sentence I impose here has no relation to any brutalities that may have been involved in this defendant's treatment of American prisoners of war.

The punishment inflicted by the common law when traitors were publicly dragged to the place of execution and there drawn, quartered and beheaded recalls the extreme odium which our forebears attached to the crime of betraying one's country.

As it has been truly said: "It is the essence of treachery that those who commit it would still be severely punished if the law forgot its duty to provide deterrents to crime and did not lay a finger on them."

Haunting him to the end of his days would be the memory not only of his base treason against the land of his birth, but also of Sadao Munemori who won the Congressional Medal of Honor; of Privates First Class, Fumitaka Nagato and Saburo Tanamachi, who are buried with the American heroes of all time at Arlington National Cemetery; and the memory of almost seven hundred other boys of like American birthright, of like Japanese parentage, who stood the supreme test of loyalty to their native land, and gave up their lives that America and her institutions might continue to live.

Considering the inherent nature of treason and the purpose of the law in imposing punishment for the crime, reflection leads to the conclusion that the only worth-while use for the life of a traitor, such as this defendant has proved himself to be, is to serve as an example to those of weak moral fiber who may hereafter be tempted to commit treason against the United States.Kawakita's mother broke down after hearing the sentence, and her son begged her not to kill herself.

[1] In a 4–3 decision issued on June 2, 1952, the Supreme Court upheld Kawakita's treason conviction and death sentence.

The Court's majority held that the jury in Kawakita's trial had been justified in concluding that he had not lost or given up his U.S. citizenship while he was in Japan during the war.

[5][1]: 732–736  Further, given the flagrant nature of Kawakita's actions, the majority found that the trial judge had not acted arbitrarily in imposing a death sentence.

The dissent concluded that "for over two years, [Kawakita] was consistently demonstrating his allegiance to Japan, not the United States.

[5][1]: 746 On October 29, 1953, President Dwight D. Eisenhower, responding to appeals from the Japanese government commuted Kawakita's sentence to life imprisonment plus a $10,000 fine.

However, on October 24, 1963, President Kennedy ordered his release on the condition that he permanently leave the United States.

Mathes was adamantly opposed, but James Carter supported clemency, as did the lower appellate judge who wrote the opinion upholding Kawakita's conviction.

On October 24, 1963, President John F. Kennedy—in what would be one of his last official acts before his assassination—ordered Kawakita released from prison on the condition that he leave the United States and be banned from ever returning.

[14]: 431  In 1978, Kawakita sought permission to travel to the United States to visit his parents' grave, but his efforts were unsuccessful.