50 C.F.R. § 402.15 : Wildlife and Fisheries — JOINT REGULATIONS (UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR AND NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE); ENDANGERED SPECIES COMMITTEE REGULATIONS —Subchapter A — INTERAGENCY COOPERATION-ENDANGERED SPECIES ACT OF 1973, AS AMENDED — CONSULTATION PROCEDURES — Responsibilities of Federal agency following issuance of a biological opinion

(a) Following the issuance of a biological opinion, the Federal agency shall determine whether and in what manner to proceed with the action in light of its section 7 obligations and the Service's biological opinion.
(b) If a jeopardy biological opinion is issued, the Federal agency shall notify the Service of its final decision on the action.
(c) If the Federal agency determines that it cannot comply with the requirements of section 7(a)(2) after consultation with the Service, it may apply for an exemption. Procedures for exemption applications by Federal agencies and others are found in 50 CFR part 451.

50 C.F.R. §402.15