16 U.S.C. § 429b-2
Subsequent to October 13, 1980, the owner of improved property on the date of its acquisition by the Secretary may, as a condition of such acquisition, retain for himself and his heirs and assigns a right of use and occupancy of the improved property for noncommercial residential purposes for a definite term of not more than twenty-five years or for a term ending at the death of the owner or the death of the spouse of the owner, whichever is later. The owner shall elect the term to be reserved. Unless this property is wholly or partially donated to the United States, the Secretary shall pay the owner an amount equal to the fair market value of the property on the date of its acquisition less the value on such date of the right retained by the owner. If such property is donated (in whole or in part) to the United States, the Secretary may pay to the owner such lesser amount as the owner may agree to. A right retained pursuant to this section shall be subject to termination by the Secretary upon his determination that it is being exercised in a manner inconsistent with the purposes of sections 429b to 429b-5 of this title, and it shall terminate by operation of law upon the Secretary's notifying the holder of the right of such determination and tendering to him an amount equal to the fair market value of that portion of the right which remains unexpired.
No property owner who elects to retain a right of use and occupancy under this section shall be considered a displaced person as defined in section 4601(6) of title 42. Such owners shall be considered to have waived any benefits which would otherwise accrue to them under sections 4623 to 4626 of title 42.
16 U.S.C. § 429b-2