((a)) ** Equitable relief; case or controversy; district court jurisdiction** Except as provided in subsection (b) of this section, any person may commence a civil action for equitable relief on his own behalf, whenever such action constitutes a case or controversy—

((1)) against any person (including (A) the United States, and (B) any other governmental instrumentality or agency to the extent permitted by the eleventh amendment to the Constitution) who is alleged to be in violation of any provision of this chapter or any condition of a license issued pursuant to this chapter; or

((2)) against the Secretary where there is alleged a failure of the Secretary to perform any act or duty under this chapter which is not discretionary with the Secretary. Any action brought against the Secretary under this paragraph shall be brought in the district court for the District of Columbia or the district of the appropriate adjacent coastal State.

((b)) ** Notice; intervention of right by person** No civil action may be commenced—

((1)) under subsection (a)(1) of this section—

((A)) prior to 60 days after the plaintiff has given notice of the violation (i) to the Secretary and (ii) to any alleged violator; or

((B)) if the Secretary or the Attorney General has commenced and is diligently prosecuting a civil or criminal action with respect to such matters in a court of the United States, but in any such action any person may intervene as a matter of right; or

((2)) under subsection (a)(2) of this section prior to 60 days after the plaintiff has given notice of such action to the Secretary.

((c)) ** Intervention of right by Secretary or Attorney General** In any action under this section, the Secretary or the Attorney General, if not a party, may intervene as a matter of right.

((d)) ** Costs of litigation; attorney and witness fees** The Court, in issuing any final order in any action brought pursuant to subsection (a) of this section, may award costs of litigation (including reasonable attorney and expert witness fees) to any party whenever the court determines that such an award is appropriate.

((e)) ** Statutory or common law rights unaffected** Nothing in this section shall restrict any right which any person (or class of persons) may have under any statute or common law to seek enforcement or to seek any other relief.