Implicit in the term ‘national defense’ is the notion of defending those values and ideas which set this Nation apart. . . . It would indeed be ironic if, in the name of national defense, we would sanction the subversion of . . . those liberties . . . which makes the defense of the Nation worthwhile.
- Justice Earl Warren, U.S. v. Robel, 389 U.S. 258 (1967)