Nothing contained in this chapter, except as otherwise provided herein, shall be construed—

(a) To prevent or interfere with the enforcement of, or the procedure under, the provisions of the Act entitled “An Act to protect trade and commerce against unlawful restraints and monopolies,” approved July 2, 1890, the Act entitled “An Act to supplement existing laws against unlawful restraints and monopolies, and for other purposes,” approved October 15, 1914, the Interstate Commerce Act as amended, the Act entitled “An Act to promote export trade, and for other purposes,” approved April 10, 1918 [15 U.S.C. 61 et seq.] or sections 73 to 76, inclusive, of the Act of August 27, 1894, entitled “An Act to reduce taxation, to provide revenue for the Government, and for other purposes,” as amended by the Act entitled “An Act to amend sections seventy-three and seventy-six of the Act of August twenty-seventh, eighteen hundred and ninety-four, entitled ‘An Act to reduce taxation, to provide revenue for the Government, and for other purposes,’ ” approved February 12, 1913, or

(b) To alter, modify, or repeal such Acts or any part or parts thereof, or

(c) To prevent or interfere with any investigation, proceeding, or prosecution begun and pending on August 15, 1921.