concurring.
I deem it important to state what I understand to be the Court’s holding. Agreeing with its holding, I join its opinion.
The power of the Congress to punish for contempt of its authority is, as the Court points out, rooted in history. It has been acknowledged by this Court since 1821. Anderson v. Dunn, 6 Wheat. 204. Until 1857, Congress was content to punish for contempt through its own process. By the Act of January 24, 1857, 11 Stat. 155, as amended by the Act of January 24, 1862, 12 Stat. 333, Congress provided that, “in addition to the pains and penalties now existing” (referring of course to the power of Congress itself to punish for contempt), “contumacy in a witness called to testify in a matter properly under consideration by either House, and deliberately refusing to answer questions pertinent thereto, shall be a misdemeanor against the United States.” In re Chapman, 166 U. S. 661, 672. This legislation is now 2 U. S. C. § 192. By thus making the federal judiciary the affirmative agency for enforcing the authority that underlies the congressional power to punish for contempt, Congress necessarily brings into play the specific provisions of the Constitution relating to the prosecution of offenses and those implied restrictions under which courts function.
*217To turn to the immediate problem before us, the scope of inquiry that a committee is authorized to pursue must be defined with sufficiently unambiguous clarity to safeguard a witness from the hazards of vagueness in the enforcement of the criminal process against which the Due Process Clause protects. The questions must be put with relevance and definiteness sufficient to enable the witness to know whether his refusal to answer may lead to conviction for criminal contempt and to enable both the trial and the appellate courts readily to determine whether the particular circumstances justify a finding of guilt.
While implied authority for the questioning by the Committee, sweeping as was its inquiry, may be squeezed out of the repeated acquiescence by Congress in the Committee’s inquiries, the basis for determining petitioner’s guilt is not thereby laid. Prosecution for contempt of Congress presupposes an adequate opportunity for the defendant to have awareness of the pertinency of the information that he has denied to Congress. And the basis of such awareness must be contemporaneous with the witness’ refusal to answer and not at the trial for it. Accordingly, the actual scope of the inquiry that the Committee was authorized to conduct and the relevance of the questions to that inquiry must be shown to have been luminous at the time when asked and not left, at best, in cloudiness. The circumstances of this case were wanting in these essentials.