The Secretary of the Interior is authorized to execute on behalf of the United States all necessary deeds and leases to effect the purposes of sections 459r to 459t of this title. Every such deed or lease shall contain the express condition that the grantee or lessee shall use the property exclusively for public park, recreational, and conservation purposes, and the further express condition that the United States assumes no obligation for the maintenance or operation of the property after the acceptance of such deed or during the term of such lease, and may contain such other conditions not inconsistent with such express conditions as may be agreed upon by the Secretary and the grantee or lessee: Provided, That the title and right to possession of any lands so conveyed or leased, together with the improvements thereon, shall revert to the United States upon a finding by the Secretary, after notice to such grantee or lessee and after an opportunity for a hearing, that the grantee or lessee has not complied with such conditions during a period of more than three years, which finding shall be final and conclusive, and such lands and improvements thereon, upon such reversion to the United States, shall be returned to the jurisdiction of the Department of the Interior and upon determination of the Secretary may be considered as surplus real property to be disposed of in accordance with section 1303 of title 40.