Notwithstanding any other provision of law, or any authorization heretofore given pursuant to law, the Federal Energy Regulatory Commission may not license the construction of any dam, water conduit, reservoir, powerhouse, transmission line, or other project work under the Federal Power Act (41 Stat. 1063
), as amended (16
et seq.), within the recreation area: Provided, That the provisions of the Federal Power Act (41 Stat. 1063
) shall continue to apply to any project (as defined in such Act), and all of the facilities and improvements required or used in connection with the operation and maintenance of said project, in existence within the recreation area which project is already constructed or under construction on December 31, 1975.