Four major court cases testing the constitutionality of wartime treatment of Japanese American citizens reached the U.S. Supreme Court in 1943 and 1944. Lawsuits brought by Minoru Yasui, Gordon K. Hirabayashi, and Fred T. Korematsu related to violations of curfew and other discriminatory regulations imposed on Japanese Americans prior to relocation.

In these cases, the justices chose to rule narrowly on the specific issues, rather than consider larger Constitutional issues of relocation. Accepting government justifications of national security and military necessity, the Supreme Court refused to block Executive Order 9066 and the programs it generated.

Gordon Hirabayashi: Violation of Exclusion Order (oral history transcript)

Mitsuye Endo's case challenged the public law of March 21, 1942, which empowered military authorities to impose a curfew, but did not mention detention. The Supreme Court ruled that military authorities had exceeded the scope of the law by imprisoning loyal American citizens. Ms. Endo and other internees could not be barred from access to writs of habeas corpus — the Constitution's guarantee to a swift hearing in which specific accusations would have to be stated.

The US Supreme Court justices who ruled on the four cases were divided over the constitutional issues in question. These differences were reflected in the legal opinions they offered on the Japanese American cases.

"We must credit the military with as much good faith as we would any other public official. We cannot sit in judgment of the military requirements of that hour."
—Associate Justice William O. Douglas, Concurring Opinion, Hirabayashi v. U.S., 1943

"The broad provisions of the Bill of rights... are [not] suspended by the mere existence of a state of war. Distinctions based on color and ancestry are utterly inconsistent with our traditions and ideals. Today is the first time, so far as I am aware, that we have sustained a substantial restriction of the personal liberty of citizens based on the accident of race or ancestry. It bears a melancholy resemblance to the treatment accorded to members of the Jewish race in Germany. This goes to the very brink of constitutional power."
—Associate Justice Frank Murphy, Concurring Opinion, Hirabayashi v. U.S., 1943

"This is not a case of keeping people off the streets at night as was Hirabayashi...It is a case of convicting a citizen ... for not submitting to imprisonment in a concentration camp solely because of his ancestry."
—Associate Justice Owen J. Roberts, Dissenting Opinion, Korematsu v. U.S., 1944

"[There have to be] definite limits to military discretion, especially where martial law has not been declared. Individuals must not be impoverished of their constitutional rights on a plea of military necessity that has neither substance nor support." —Associate Justice Frank Murphy, Concurring Opinion, Ex Parte Endo, 1944

As early as 1945 Eugene V. Rostow of the Yale Law School Faculty referred to the Supreme Court decisions as "our worst wartime mistake." "The basic issues," he urged, "should be presented to the Supreme Court again, in an effort to obtain a reversal of these wartime decisions." In American law, however, the principle of finality normally bars a reconsideration of a Supreme Court decision. Reinterpretation of the Court's decision usually occurs in another case covering the same legal principle. The incarceration of Japanese Americans was, however, a unique event. As a Presidential Commission noted in 1980, "the country has not been so unfortunate that a repetition of the facts has occurred to give the Court that opportunity."

In belated recognition of the injustice done to the innocent Japanese Americans, President Gerald R. Ford made a formal apology to them in 1976.

Sue Embrey: To Correct Democracy (oral history transcript)

In January 1983, a legal team filed a writ of coram nobis, offering them the possibility of overturning the 1944 decisions of the Supreme Court, which seeks to correct an injury caused by a mistake of the court. The writ charged that in 1943-1944 federal officials had deliberately altered, suppressed, and concealed crucial evidence in prosecuting the case against Fred Korematsu. Similar writs were later filed on behalf of Minoru Yasui and Gordon Hirabayashi.

Minoru Yasui died before action was taken in his case. In 1984, the U.S. District Court for Northern California set aside Fred Korematsu's 1944 conviction. Three years later, the United States Court of Appeals for the Ninth District handed down a similar decision in the Hirabayashi case. As a result of these decisions, the Supreme Court of the United States did not have an opportunity to reverse the original 1944 rulings on the basic constitutional issues involved.