The United States and Zimbabwe are parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora. The Convention regulates the international trade of imperiled species that are listed in its appendices, which include African elephants. Parties to the Convention may not allow trade in species listed in the appendices except in accordance with the treaty's provisions. It is undisputed that the proscriptions in the Convention are a floor, not a ceiling, for the protection of Appendix II species. The Parties are free to adopt . . . stricter domestic measures regarding the conditions for trade, taking possession or transport of specimens of species included in Appendices I, II, and III, or the complete prohibition thereof. Congress passed the Endangered Species Act (ESA). The Act generally prohibits the importation of endangered species into the United States. For threatened species, section 4(d) requires D to 'issue such regulations as [it] deems necessary and advisable to provide for their conservation.' §1533(d). D has promulgated a regulation extending the general import prohibition on endangered species to threatened species. D reserved the right to create 'special rule[s]' regarding threatened species, which 'contain all the applicable prohibitions and exceptions' regarding the import of that species. D established a regime in which the prohibitions established for endangered species are extended automatically to all threatened species by a blanket rule and then withdrawn as appropriate, by special rule for particular species, and by permit in particular situations. Since 1978, D has listed the African elephant as a threatened species under the ESA. Since 1978, D maintained a Special Rule governing elephant importation. In 1992, D added a provision to the Special Rule providing that sport-hunted African elephant trophies may only be imported into the United States under certain conditions, including that D must make '[a] determination . . . that the killing of the trophy animal will enhance the survival of the species.' The enhancement finding requirement continues to apply in accordance with the Special Rule under the ESA. D maintains the right to make nation-wide enhancement findings sua sponte, 'on a periodic basis upon receipt of new information on the species' population or management.' Section 9(c)(2) of the ESA provides that 'any importation into the United States' of non-endangered, Appendix II species such as Zimbabwean elephants 'shall,' where certain conditions are satisfied, 'be presumed to be an importation not in violation of any provision of [the ESA] or any regulation issued pursuant to [the ESA].' §1538(c)(2). In 1997, D made a positive enhancement finding for the sport hunting of African elephants in Zimbabwe. D explained that revenues generated by sport hunting benefited rural communities and elephant conservation programs in Zimbabwe. Zimbabwe's government had in place conservation and anti-poaching programs to protect the elephants. And 'one of the best sets of elephant population data in Africa' indicated that Zimbabwe's elephant population was growing at 'about 5% per annum,' from 46,000 elephants in 1980 to 66,000 in 1997. D found that 'the import of sport-hunted elephant trophies from Zimbabwe enhances the survival of the species.' On April 4, 2014, D made an interim negative enhancement finding and suspended the importation of sport-hunted elephant trophies from Zimbabwe. 'The elephant population in Zimbabwe has declined from 84,416 elephants in 2007 to 47,366 elephants in 2012.' From a lack of data, D determined that it was not possible 'to make a positive finding that sport-hunting is enhancing the survival of the species.' D temporarily banned imports of sport-hunted trophies of elephants from Zimbabwe until better information could be obtained from the Zimbabwean government. The Service announced the negative enhancement finding on April 4, 2014, but did not publish notice of the finding in the Federal Register until May 12, 2014. D issued a final negative enhancement finding on July 17, 2014. Unable to make a positive enhancement finding on the basis of the new information, D forbid the importation of elephants harvested in Zimbabwe from April 4, 2014, through the end of the year. On March 26, 2015, D made yet another negative enhancement finding, banning the importation of trophies of 'elephants taken in Zimbabwe during the 2015 hunting season and future hunting seasons.' Safari Club International (Safari) and the National Rifle Association (NRA) (Ps') filed suit in District Court to challenge the 2014 and 2015 findings. Ps claimed that the agency's actions were arbitrary and capricious and violated the Endangered Species Act because to ban the elephant imports, D impermissibly relied on standards that are more stringent than the statutory requirements in the ESA. Ps claimed that the removal of the enhancement-finding requirement from the Convention in 1994 required the Service to initiate rule-making with respect to the Special Rule's enhancement condition. Ps contend that the three enhancement findings were rules subject to notice-and-comment rule-making procedures under § 553 of the APA. D claimed the rule was an adjudication and therefore was not subject to the APA's rule-making requirements. The District Court agreed with D and denied Ps' motion for summary judgment on these claims and granted judgment to D. Ps appealed.