This is a proceeding pursuant to § 14 (a) of the Subversive Activities Control Act of 1950 to review an order of the Subversive Activities Control Board requiring the Communist Party of the United States to register as a Communist-action organization under § 7 of the Act. The United States Court of Appeals for the District of Columbia has affirmed the Board's registration order. Because important questions of construction and constitutionality of the statute were raised by the Party's petition for certiorari, we brought the case here. 361 U. S. 951.