The citizen-suit provision allows individuals to bring suits ???to enjoin any person, including the United States and any other governmental instrumentality or agency ... who is alleged to be in violation of any provision of this chapter or regulation issued under authority thereof.??? Id.; see Bennett v. Spear, 520 U.S. 154, 173, 117 S.Ct. 1154, 137 L.Ed.2d 281 (1997); Washington Toxics Coal. v.