That for the purposes of acquiring non-Federal lands within the boundaries of said park as established by this subchapter, the Secretary of the Interior is authorized, in his discretion, to exchange federally owned lands within the Roosevelt recreational demonstration area project, located outside the boundaries of the park for State or privately owned lands of approximately equal value within the boundaries of the park, when in his opinion such action is in the interest of the United States, the title to any lands acquired under this section to be satisfactory to the Attorney General. Upon the vesting of title thereto in the United States, any lands acquired pursuant to this authorization shall become a part of the park and shall be subject to the laws applicable thereto.