with whom Mr. Justice Brennan joins, concurring.
While joining the opinion of the Court, I add a brief word. The Court has never held, and does not hold today, that the antitrust laws are inapplicable to anti-competitive conduct simply because a federal agency has jurisdiction over the activities of one or more of the defendants. An implied repeal of the antitrust laws may be found only if there exists a “plain repugnancy between the antitrust and regulatory provisions.” United States v. Philadelphia Nat. Bank, 374 U. S. 321, 351.
The mere existence of the Commission’s reserve power of oversight with respect to rules initially adopted by the exchanges, therefore, does not necessarily immunize those rules from antitrust attack. Rather, “exchange self-regulation is to be regarded as justified in response to antitrust charges only to the extent necessary to protect the achievement of the aims of the Securities Exchange Act.” Silver v. New York Stock Exchange, 373 *693U. S. 341, 361. The question presented by the present case, therefore, is whether exchange rules fixing minimum commission rates are “necessary to make the Securities Exchange Act work.” Id., at 357.
As the Court’s opinion explains, see ante, at 663-667, when Congress enacted the Securities Exchange Act of 1934, it was fully aware of the well-established exchange practice of fixing commission rates, which had existed continuously since 1792. Nevertheless, Congress chose not to prohibit that practice. Instead, in § 19 (b) (9) of the 1934 Act Congress specifically empowered the Commission to exercise direct supervisory authority over exchange rules respecting “the fixing of reasonable rates of commission.” Congress thereby unmistakably determined that, until such time as the Commission ruled to the contrary, exchange rules fixing minimum commission rates would further the policies of the 1934 Act. Accordingly, although the Act contains no express exemption from the antitrust laws for exchange rules establishing fixed commission rates, under Silver that particular in-, stance of exchange self-regulation is immune from antitrust attack.