An aggrieved person may commence a civil action under this subsection whether or not a complaint has been filed under
section 3610(a) of this title and without regard to the status of any such complaint, but if the Secretary or a State or local agency has obtained a conciliation agreement with the consent of an aggrieved person, no action may be filed under this subsection by such aggrieved person with respect to the alleged discriminatory housing practice which forms the basis for such complaint except for the purpose of enforcing the terms of such an agreement.