A brief summary of a reading of the above doocumments posted by me by Alamo-Girl.
The Endangered Species Act (ESA) effectively bypasses the normal authority of the Executive and Legislative branches of federal government. It does this by allowing law to be made by the courts with reimbursements made to trial attorneys by the government. Of course, judicial rulings vary in different parts of the country, so the law has not been consistently developed or enforced.
Notably, in Bennet v. Plenert 63 F. 3rd 915 - which was decided by the 9th Circuit Court of Appeals in August of 1995 the court made it very clear that the law itself does not protect other parties, such as irrigators. The court found that the plaintiffs lacked standing because of the zone of interest test. The plaintiff had to be within the zone of interest intended by Congress to be protected by the law. And the ESA is limited to protecting only plaintiffs who allege an interest in the preservation of an endangered species.
It therefore seems that a successful cause of action against environmentalists would have to be under some other provision of the law something like fraud for junk science or interference with contracts for irrigators, and so on. The successful plaintiff must show actual damages, so it appears the best lawsuit opportunity would follow a damaging green decision previously determined under the under the ESA. Klamath is a good case where actual damages can be shown.