Simpson's hallmark legislation in the House of Representatives has been the Central Idaho Economic Development and Recreation Act (CIEDRA), which would create 312,000 acres of wilderness in central Idaho, much of which is currently a wilderness study area. Simpson has faced substantial resistance from groups like the Sierra Club who claim the bill lacks "wilderness values" because the bill allows for motorized access to certain portions of the wilderness area and some federal land would be transferred to the State of Idaho to promote the economic development of the local community and the recreational use of National Forest land and other public lands in central Idaho. Simpson has also faced opposition from groups who oppose new federal land designations, and wilderness designations particularly because of restricted access to wilderness areas. In August 2015 a revised version of CIEDRA, the Sawtooth National Recreation Area and Jerry Peak Wilderness Additions Act, passed Congress and was signed by President Obama, creating the Hemingway–Boulders, Jim McClure–Jerry Peak, and White Clouds wilderness areas, which cover a total of 275,665 acres (111,558 ha) of central Idaho.