(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.

In suits brought under this chapter, the district court shall have jurisdiction, without regard to the amount in controversy or the citizenship of the parties, to enforce any provision of this chapter or any condition of a license issued pursuant to this chapter, or to order the Secretary to perform such act or duty, as the case may be.

(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.

Notice under this subsection shall be given in such a manner as the Secretary shall prescribe by regulation.

(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.