After very extensive hearings under the Subversive Activities Control Act of 1950, the Board in 1953 found that the Communist Party of the United States was a "Communist-action organization," within the meaning of the Act, and ordered it to register as such under 7. A remand of the case by this Court, 351 U.S. 115, and a second remand by the Court of Appeals led to further proceedings before the Board, involving rulings on additional procedural points and two reconsiderations of the entire record, following which the Board adhered to its conclusion. After denial of motions made by the Party under 14 (a) and after review on the merits, the Court of Appeals affirmed the Boards order. Held: The judgment is affirmed. Pp. 4-115.

1. Certain procedural rulings made by the Board and the Court of Appeals do not constitute prejudicial errors requiring that this proceeding be remanded to the Board again. Pp. 22-35.

(a) A witness having been cross-examined at length following his direct testimony during the initial hearing, and the Board having stricken his testimony on two subjects about which recordings of interviews with him were discovered and produced after remand of the case, it cannot be said on this record that the Board abused its discretion in refusing to strike all of his testimony because ill [367 U.S. 1, 2] health prevented him from submitting to further cross-examination, when the Court of Appeals sustained the Boards ruling. Pp. 22-29.

(b) By failing to raise the question in its previous petition for certiorari in this Court, the Party abandoned its claim of error in the Boards denial of its motion to require production of certain memoranda prepared by a government witness, and the Party could not resurrect that claim by repeating the motion before the Board after this Courts remand of the case. Pp. 29-32.

(c) It cannot be said that the Court of Appeals abused its discretion in denying as untimely motions made by the Party under 14 (a) more than 5 years after termination of the initial hearings for orders requiring production of documents in connection with the testimony of government witnesses. Pp. 32-35.

2. The Board and the Court of Appeals did not err in their construction of the Act or in their application of it to the Party on this record. Pp. 35-69.

(a) In concluding that the Party was "substantially directed, dominated, or controlled" by the Soviet Union, within the meaning of 3 (3), the Board and the Court of Appeals did not err either in their construction of the Act or in finding that the facts shown by the record bring the Party within it. Pp. 36-55.

(b) In concluding that the Party "operates primarily to advance the objectives of [the] . . . world Communist movement," within the meaning of 3 (3), the Board and the Court of Appeals did not err either in their construction of the Act or in finding that the facts shown by this record bring the Party within it. Pp. 55-56.

(c) The Board did not misinterpret or misapply the requirement of 13 (e) that, in determining whether any organization is a Communist-action organization, it shall "take into consideration" the "extent to which" such organization engages in certain classes of conduct specified therein; nor did it abuse its discretion in its rulings on the admissibility of evidence and objections to questions asked on cross-examination in this connection. Pp. 56-66.

(d) The action of the Court of Appeals in striking one subsidiary finding of the Board did not require another remand of the proceedings to the Board. Pp. 66-67.

(e) Though the Boards description of "the world Communist movement" to which its findings related the Party did not [367 U.S. 1, 3] duplicate in all details the description contained in 2 of the Act, it was the one meant by Congress. Pp. 68-69.

(f) The Board and the court below did not err in relying on evidence of the