The U.S. Court of Appeals for the Ninth Circuit decided an interesting Endangered Species Act (ESA) case this week. San Luis Obispo Coastkeeper v. County of San Luis Obispo, No. 24-7807 (9th Cir. Dec. 3, 2025).
Certain environmental NGO’s claimed that San Luis Obispo County’s operation of a dam potentially harms the steelhead trout, a fish listed as threatened under the ESA. Plaintiffs sought a mandatory preliminary injunction directing changes in the dam’s water flow operation to help the trout. The county opposed, arguing that the mandated operational changes would harm the California red-legged frog and the tidewater goby, both of which live in the same habitat and are listed as endangered under the ESA. The district court granted the injunction without considering the impact on the frog and the goby. The Ninth Circuit reversed.
The appellate court noted that, in ESA cases, only the first two parts of the four-part standard for an injunction – (1) probability of success, (2) irreparable harm, (3) balance of the equities; (4) public interest – apply. This is because, in line with the famous “snail darter” case – TVA v. Hill, 437 U.S. 153 (1978) – Congress has already balanced the equities in favor of the listed species which take precedence over other competing equities “whatever the cost.” So, if there is probability of a take, then the endangered species at issue wins, regardless of how the relief impacts other interests. However, in a case like this one where the relief in favor of one listed species will affirmatively harm other listed species, the TVA rationale “collapses.” Slip op. at 19. In such a case, “[t]he exception to the traditional test, created in TVA, does not apply. The court must balance the equities and consider the public interest as to the other listed species.” Slip op. at 20.
So far so good. But how is a court supposed to do this? The district court here directed the parties to work it out with the National Marine Fisheries and U.S. Fish and Wildlife Services, but those agencies declined to get involved. So now it’s up to the district court. The guidance from the Ninth Circuit was not particularly illuminating:
Species are interconnected. Sometimes, what looks harmful to one species in the short term may benefit it, or others, in the long run. And if there is no way to reconcile the risks to multiple listed species, the equities and public interest in species conservation, to which the ESA gave precedence, do not counsel a single outcome and judgments may need to be made about the relative strength of these considerations in relation to the protected species at issue. [Slip op. at 21].
In other words, do your best. But this can get tricky. As the concurring opinion observed, it may turn out to be a “zero sum game.” Slip op. at 27. Steelheads actually eat red-legged frog tadpoles and gobies, so relief that preserves more trout means that more red-legged frogs and gobies may become trout breakfast. Moreover, the steelhead is threatened while the red-legged frog and goby are endangered. When push comes to shove on who gets to survive, does the threatened species have to give way to the endangered one? This Solomonic decision is left to the district court.
