Defenders of Wildlife v. Hall

The Northern Rocky Mountain gray wolf was listed as an endangered species under the Endangered Species Act in 1974. In 1987, the United States Fish & Wildlife Service (the service) (defendant) developed a recovery plan for these wolves in the Montana, Idaho, and Wyoming area. This plan used wolf numbers as the criteria for determining when the wolves were no longer endangered. In 1994, the service conducted a study and used the results to revise the criteria. The new criteria required higher wolf numbers and genetic mixing of the three core wolf populations before the species would be considered out of danger. Several years later, the service conducted another evaluation and affirmed the criteria for considering the wolf no longer endangered. For eight years, the wolf populations hit the listed numbers, but there was no evidence that the different core populations were mixing genetically. The service decided that the genetic-intermixing requirement was not truly necessary and began the process of taking the wolves off the endangered-species list, including getting plans from the three states for managing the wolves once they were delisted. Montana’s and Idaho’s plans seemed to be compatible with the continued survival of the species in those states. However, among other issues, Wyoming’s plan did not commit to maintaining any minimum number of wolves and allowed people to kill wolves if they believed the wolf was damaging property in any way. This plan was potentially incompatible with long-term survival of the gray wolf species in Wyoming. Regardless, the service accepted the plans and removed the gray wolf from the endangered-species list. Defenders of Wildlife and others (plaintiffs) sued the service, challenging its decision to delist the gray wolf and asking for a preliminary injunction putting the wolves back on the endangered-species list while the lawsuit was pending.