; or (2) the actions, operations, or other requirements that the amendment would remove are no longer warranted. (b) Restriction on amendments The process described in subsection (a) shall be the only method by which the Secretaries may operate the FCRPS during the time period established under section 2 in any way that is not consistent with the reasonable and prudent alternatives set forth in the Supplemental Opinion. 4. Limitation on restricting FCRPS electrical generation or navigation on the Snake River No structural modification, action, study, or engineering plan that restricts electrical generation at any Federal Columbia Power System hydroelectric dam, or that limits navigation on the Snake River in the State of Washington, Oregon, or Idaho, shall proceed unless such proposal is specifically and expressly authorized by an Act of Congress enacted after the date of submission to Congress of a proposal for such modification, action, study, or engineering plan, respectively.