50 CFR § 424.20 - Emergency rules.
(a) Sections 424.16, 424.17, 424.18, and 424.19 notwithstanding, the Secretary may at any time issue a regulation implementing any action described in § 424.10 in regard to any emergency posing a significant risk to the well-being of a species of fish, wildlife, or plant. Such rules shall, at the discretion of the Secretary, take effect immediately on publication in the Federal Register. In the case of any such action that applies to a resident species, the Secretary shall give actual notice of such regulation to the State agency in each State in which such species is believed to occur. Publication in the Federal Register of such an emergency rule shall provide detailed reasons why the rule is necessary. An emergency rule shall cease to have force and effect after 240 days unless the procedures described in §§ 424.16, 424.17, 424.18, and 424.19 (as appropriate) have been complied with during that period.
(b) If at any time after issuing an emergency rule, the Secretary determines, on the basis of the best scientific and commercial data available, that substantial evidence does not then exist to warrant such rule, it shall be withdrawn.