16 U.S.C. § 460s-9
The Secretary shall be prohibited from acquiring by condemnation any (1) improved property within the inland buffer zone or (2) property within the inland buffer zone during all times when, in his judgment, such property is being used (A) for the growing and harvesting of timber under a scientific program of selective cutting and forest management, or (B) for commercial purposes, if such commercial purposes are the same such purposes for which such property is being used on December 31, 1964, so long as the use of such improved or other property would further the purposes of this subchapter and such use does not impair the usefulness and attractiveness of the lakeshore.
As used in this subchapter, the term "improved property" shall mean any one-family dwelling on which construction was begun before December 31, 1964, together with so much of the land on which the dwelling is situated (such land being in the same ownership as the dwelling) as shall be reasonably necessary for the enjoyment of the dwelling.
16 U.S.C. § 460s-9