; and (ii) the alleged violator; or (B) if the Department of Justice has commenced action to impose a civil fine under subsection (a). (4) Intervention In any suit under this subsection in which the United States is not a party, the Attorney General may intervene on behalf of the United States as a matter of right. (5) Costs of litigation The court, in issuing any final order in any suit brought under this subsection, may award costs of litigation (including reasonable attorney and expert witness fees) to any party, if the court determines the award is appropriate.