Korematsu v. United States was a Supreme Court case that upheld the forced relocation and internment of Japanese Americans during World War II. The Court ruled that the need to protect against espionage and sabotage outweighed the individual rights of Japanese Americans. The petitioner, a Japanese American citizen, was convicted for violating a Civilian Exclusion Order that excluded all persons of Japanese ancestry from a "Military Area" in California. The Court upheld the conviction, citing pressing public necessity as justification for the restriction. The Act of Congress of March 21, 1942, made it a misdemeanor for anyone to violate any military order or restriction applicable to a military area or zone prescribed by the Secretary of War or any military commander designated by the Secretary of War. The Court had previously upheld a conviction for violating a curfew order, which was based on the same 1942 Congressional Act and executive and military orders, in Hirabayashi v. United States. The constitutionality of the Act and orders was challenged, but the Court upheld them as necessary measures to prevent espionage and sabotage in areas threatened by Japanese attack. The decision in Korematsu v. United States has since been widely criticized and is considered a stain on the history of civil liberties in the United States.

In the case of Korematsu v. United States, Justice Frankfurter agrees that military orders are constitutional if they are reasonably expedient and appropriate for conducting war, while Justice Roberts dissents, arguing that the petitioner's Constitutional rights were violated. The petitioner, a US citizen of Japanese ancestry, was excluded from Military Area No. 1 due to Executive Order No. 9066 and subsequent proclamations. The lower court did not err in convicting him of violating an exclusion order, but Justice Murphy dissents, arguing that the exclusion of all persons of Japanese ancestry is unconstitutional and racist, and takes away their constitutional rights. The forced exclusion of people of Japanese descent was largely based on the erroneous assumption of racial guilt rather than military necessity.

The report justifying the exclusion of Japanese Americans is based on questionable racial and sociological grounds, violating individual rights under the law. The lower court erred by not recognizing the lack of justification for the government's actions. The dissenting opinion questions the constitutionality of military orders that made non-criminal conduct a crime and required detention, emphasizing the importance of protecting individual rights and freedoms. The argument challenges the constitutionality of Korematsu's conviction based on his Japanese ancestry and questions the constitutionality of military orders. The judgment should be reversed, and the prisoner should be discharged.