remained subject to antitrust action by the Department of Justice. Although we are not unmindful of the disfavor with which antitrust exemption is generally regarded, see, e. g., California v. Federal Power Commission, 369 U.S. 482, 82 S.Ct. 901, 8 L.Ed.2d 54 (1962), we perceive significant differences between Philadelphia National Bank and the case which we today decide. AVe note that the history of the Bank Merger Act evidenced a congressional intent not to immunize bank mergers from at least Sherman Act attack, see 374 U.S. at 352, 83 S.Ct. 1715, whereas the 1934 Act entrusts the SEC with supervision of rate-fixing, a practice which outside the confines of the 1934 Act is a per se violation of the Sherman Act. Cf. Silver v. New York Stock Exchange, 373 U.S. at 347-349, 86 S.Ct. 1246
recognizing that a group boycott carried out within the framework of the 1934 act is not a per se antitrust violation holding that violation of city ordinance does not constitute negligence per se holding that the per se rule does not apply to a vertical agreement between a buyer and supplier and noting that precedent limits the per se rule in the boycott context to cases involving horizontal agreements among direct competitors holding that violation of state law was not a per se constitutional violation holding a concerted boycott to be a per se violation of  1 of the sherman act