Nothing in sections 9 to 15 of this title shall be construed to affect or impair the right of Congress, at any time hereafter, to alter, amend, or repeal sections 1 to 6 and 8 (!1) of this title; and sections 9 to 15 of this title shall be subject to alteration, amendment, or repeal as, in the opinion of Congress, justice or the public welfare may require; and nothing herein contained shall be held to deny, exclude, or impair any right or remedy in the premises now or hereafter existing in the United States, or the authority of the Federal Communications Commission under the provisions of the Communications Act of 1934, as amended [47 U.S.C. 151 et seq.], to prescribe charges, classifications, regulations, and practices, including priorities, applicable to Government communications.