In Kawakita v. United States, the U.S. Supreme Court ruled in 1951 that dual citizens owe full allegiance to the United States and can be prosecuted for treason if they act against its interests. The case involved Tomoya Kawakita, a Japanese-American citizen who was accused of mistreating American prisoners of war while working as an interpreter at a Japanese camp during World War II. After returning to America after the war, he was convicted of eight counts of treason and sentenced to death by a federal court in California. Kawakita appealed his conviction on grounds that he had lost his U.S citizenship when he registered as a national with Japan during wartime; thus could not commit treason against it. However, the Supreme Court upheld his conviction stating that despite registering as a national with Japan, Kawakita remained an American citizen since there were no formal renunciation procedures followed or approved by any US official which would have led him losing his US citizenship status.

In the dissenting opinion for Kawakita v. United States, Justice Douglas argued that dual citizenship should not be used as a basis to prosecute an individual under treason laws of one country while they are residing in another. He emphasized that Tomoya Kawakita's actions during World War II were performed as a Japanese citizen living in Japan and thus he was bound by Japanese law at the time. The fact that he also held U.S citizenship did not mean he owed allegiance to America while living on foreign soil amidst war conditions where his survival might depend on compliance with local authorities. Furthermore, Douglas pointed out inconsistencies in how dual citizens were treated under American law; some being prosecuted for avoiding military service due to their other nationality, others like Kawakita being charged with treason for acting according to their non-American allegiances during wartime circumstances. This inconsistency demonstrated arbitrariness which is against principles of justice and fairness central to legal systems.