Are there limitations on the federal government’s ability to acquire lands through condemnation under the Wild & Scenic Rivers Act?

Yes. Section 6(b) of the Wild & Scenic Rivers Act specifically prohibits the use of condemnation for fee title purchase of private lands if 50 percent or more of the acreage within the boundaries on both sides of the designated river is in public ownership (i.e., owned by the federal, state, or local government). In addition, Section 6(a)(1) of the Wild & Scenic Rivers Act prohibits acquiring more than 100 acres per river mile within the corridor, which equates to a stip of land about 400-feet wide along both sides of the river. Fee title condemnation is allowed to clear title or to acquire conservation, scenic, or other types of easements reasonably necessary for public access.

Section 6(c) of the Wild & Scenic Rivers Act specifically prohibits condemnation for fee title acquisition of lands located within any incorporated city, village, or borough if suitable local zoning ordinances are in place and applicable. Although this section authorizes the appropriate Secretary to issue zoning guidelines, this has not been done due to the many other tools and incentives available, great differences among river settings, and variable local government conditions.

Source
Interagency Wild & Scenic Rivers Council