Writing for the Supreme Court in 1948 (in Chicago & Southern Air Lines v. Waterman), Justice Robert Jackson — FDR’s former attorney general and the chief prosecutor at Nuremburg — explained that decisions involving foreign policy, including alien threats to national security, are “political, not judicial” in nature. Thus, they are
wholly confided by our Constitution to the political departments of the government, Executive and Legislative. They are delicate, complex, and involve large elements of prophecy. They are and should be undertaken only by those directly responsible to the people whose welfare they advance or imperil. They are decisions of a kind for which the Judiciary has neither aptitude, facilities nor responsibility and have long been held to belong in the domain of political power not subject to judicial intrusion or inquiry.