(a) If an action under consideration by the issuer may involve “major Federal action significantly affecting the quality of the human environment” (hereinafter called “Federal action”) under the National Environmental Policy Act of 1969 (hereinafter called “NEPA”) and where there has been duly prepared under NEPA both a draft environmental impact statement and a final environmental impact statement for said action, the issuer shall have no obligation with respect to this Part except that:

Upon making the decision-making findings in accordance with section 4300.9 of this Part as provided in paragraph (1) above, or upon the supplementation of said statements as provided in paragraph (2) above, the issuer may undertake such action.

(b) If an action under consideration by the issuer involves Federal action and a written threshold determination that the action will not require a Federal impact statement, or a negative declaration, has been duly prepared pursuant to NEPA, the issuer shall have no obligation with respect to this Part provided the issuer, pursuant to the provisions of section 4300.5(c) of this Part, makes a determination that the proposed action will not have a significant effect on the environment and prepares, circulates, files and makes available for public inspection a negative declaration as provided in section 4300.5(f) and (g).