Where the land described in an allotment application pending before the Department of the Interior on or before December 18, 1971 (or such an application as adjusted or amended pursuant to subsection (b) or (c) of this section), was on that date withdrawn, reserved, or classified for powersite or power-project purposes, notwithstanding such withdrawal, reservation, or classification the described land shall be deemed vacant, unappropriated, and unreserved within the meaning of the Act of May 17, 1906, as amended, and, as such, shall be subject to adjudication or approval pursuant to the terms of this section: Provided, however, That if the described land is included as part of a project licensed under part I of the Federal Power Act of June 10, 1920 (41 Stat. 24
), as amended [16
et seq.], or is presently utilized for purposes of generating or transmitting electrical power or for any other project authorized by Act of Congress, the foregoing provision shall not apply and the allotment application shall be adjudicated pursuant to the Act of May 17, 1906, as amended: Provided further, That where the allotment applicant commenced use of the land after its withdrawal or classification for powersite purposes, the allotment shall be made subject to the right of reentry provided the United States by section 24 of the Federal Power Act, as amended [16
]: Provided further, That any right of reentry reserved in a certificate of allotment pursuant to this section shall expire twenty years after December 2, 1980, if at that time the allotted land is not subject to a license or an application for a license under part I of the Federal Power Act, as amended [16
et seq.], or actually utilized or being developed for a purpose authorized by that Act, as amended [16
et seq.], or other Act of Congress.