The Board shall immediately notify the Attorney General of any approval by it pursuant to section
1842 of this title of a proposed acquisition, merger, or consolidation transaction and, if the transaction also involves an acquisition under section
1843 of this title, the Board shall also notify the Federal Trade Commission of such approval. If the Board has found that it must act immediately in order to prevent the probable failure of a bank or bank holding company involved in any such transaction, the transaction may be consummated immediately upon approval by the Board. If the Board has advised the Comptroller of the Currency or the State supervisory authority, as the case may be, of the existence of an emergency requiring expeditious action and has required the submission of views and recommendations within ten days, the transaction may not be consummated before the fifth calendar day after the date of approval by the Board. In all other cases, the transaction may not be consummated before the thirtieth calendar day after the date of approval by the Board or, if the Board has not received any adverse comment from the Attorney General of the United States relating to competitive factors, such shorter period of time as may be prescribed by the Board with the concurrence of the Attorney General, but in no event less than 15 calendar days after the date of approval. Any action brought under the antitrust laws arising out of an acquisition, merger, or consolidation transaction approved under section
1842 of this title shall be commenced prior to the earliest time under this subsection at which the transaction approval under section
1842 of this title might be consummated. The commencement of such an action shall stay the effectiveness of the Board’s approval unless the court shall otherwise specifically order. In any such action, the court shall review de novo the issues presented. In any judicial proceeding attacking any acquisition, merger, or consolidation transaction approved pursuant to section
1842 of this title on the ground that such transaction alone and of itself constituted a violation of any antitrust laws other than section
2 of title
15, the standards applied by the court shall be identical with those that the Board is directed to apply under section
1842 of this title. Upon the consummation of an acquisition, merger, or consolidation transaction approved under section
1842 of this title in compliance with this chapter and after the termination of any antitrust litigation commenced within the period prescribed in this section, or upon the termination of such period if no such litigation is commenced therein, the transaction may not thereafter be attacked in any judicial proceeding on the ground that it alone and of itself constituted a violation of any antitrust laws other than section
2 of title
15, but nothing in this chapter shall exempt any bank holding company involved in such a transaction from complying with the antitrust laws after the consummation of such transaction.