Reasoning of the Court

The reasoning of the court that majority of the Justices were in concurring the fact that it was war time and the president has been given power to ensure a victory. Justice Frankfurter states, “The provisions of the Constitution which confer on the Congress and the President power to enable this country to wage war are as much part of the Constitution as provisions looking to a nation at peace. And we have had recent occasion to quote approvingly the statement of former Chief Justice Hughes that the war power of the Government is "the power to wage war successfully." Therefore, the validity of action under the war power must be judged wholly in the context of war. That action is not to be stigmatized as lawless because like action in times of peace would be lawless.” (http://www.law.umkc.edu/faculty/projects/ftrials/conlaw/korematsu.html)

Military authorities also stated that just having a curfew was not sufficient enough to prevent espionage. The military went as far as removing anyone with Japanese ancestry from the west coast into camps. Stated from Justice Black opinion of the court, “Nothing short of apprehension by the proper military authorities of the gravest imminent danger to the public safety can constitutionally justify either. But exclusion from a threatened area, no less than curfew, has a definite and close relationship to the prevention of espionage and sabotage. The military authorities, charged with the primary responsibility of defending our shores, concluded that curfew provided inadequate protection and ordered exclusion. They did so, as pointed out in our Hirabayashi opinion, in accordance with Congressional authority to the military to say who should, and who should not, remain in the threatened areas.”(http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=323&invol=214)