Endangered Species Act
The Endangered Species Act:  A Primer
(CRS Report for Congress 2012)
In a citizen suit, the court may grant an injunction and award attorney fees and litigation costs to any prevailing or partially prevailing party whenever the court determines such an award is appropriate.  Attorney fees will not be assessed against a citizen unless the court determines the suit is frivolous.
The Endangered Species Act authorizes citizens to enforce compliance with any provision of the Act.  16 USC § 1540(g).  This includes the prohibitions in 16 USC § 1538.  See 50 CFR § 17.21 and 50 CFR § 17.61.

Citizens must be adversely affected by the violation and normally must give 60-days notice of the alleged violation to the alleged violator and Secretary of the Interior.  This notice and delay period are intended to allow the violator an opportunity to correct his violation and to give the Secretary an opportunity to enforce compliance, thus making citizen enforcement unnecessary.