The Secretary may add a species to the lists or designate critical habitat, delete a species or critical habitat, change the listed status of a species, revise the boundary of an area designated as critical habitat, or adopt or modify special rules (see 50 CFR 17.40 - 17.48 and parts 222 and 227) applied to a threatened species only in accordance with the procedures of this part.
50 C.F.R. §424.10