42 U.S. Code § 4911 - Citizen suits
In an action under this section, the Administrator of the Environmental Protection Agency, if not a party, may intervene as a matter of right. In an action under this section respecting a noise control requirement under section 44715 of title 49, the Administrator of the Federal Aviation Administration, if not a party, may also intervene as a matter of right.
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 such an award is appropriate.
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 of any noise control requirement or to seek any other relief (including relief against an Administrator).
 So in original. Probably should be subsection “(f)”.
In subsecs. (a)(2)(B), (b)(1)(A), (c), and (f), “section 44715 of title 49” substituted for “section 611 of the Federal Aviation Act of 1958” and “such section 611” on authority of Pub. L. 103–272, § 6(b), July 5, 1994, 108 Stat. 1378, the first section of which enacted subtitles II, III, and V to X of Title 49, Transportation.