This case is here to review the judgment of the Court of Appeals for the District of Columbia affirming an order of the Subversive Activities Control Board that petitioner register with the Attorney General as a "Communist-action" organization, as required by the Subversive Activities Control Act of 1950, Title I of the Internal Security Act of 1950, 64 Stat. 987. That Act sets forth a comprehensive plan for regulation of "Communist-action" organizations. Section 2 of the Act describes a
