The Attorney General may terminate or modify a voluntary agreement, in writing, after consultation with the Chairman of the Federal Trade Commission and the sponsor of the agreement. The sponsor of the agreement, with the concurrence of or at the direction of the Administrator of the Federal Emergency Management Agency, may terminate or modify a voluntary agreement, in writing, after consultation with the Attorney General and the Chairman of the Federal Trade Commission. Any person who is a party to a voluntary agreement may terminate his participation in the agreement upon written notice to the sponsor. Any antitrust immunity conferred upon the participants in that agreement by subsection 708(j) of the DPA shall not apply to any act or omission occurring after the termination of the voluntary agreement. Immediately upon modification of a voluntary agreement, no antitrust immunity shall apply to any subsequent act or omission that is beyond the scope of the modified agreement.