January 1997 – The Center, California Public Interest Research Group, and the Wetlands Action Network filed suit to stop Steven Spielberg from building a massive development, DreamWorks Playa Vista. Without regard to the impacts on several endangered species, including the least Bell's vireo, the studio's construction was planned on one of Los Angeles' last remaining wetlands.
November 1997 – The Center threatened a lawsuit against the Army Corps of Engineers over its plan to expand the Seven Oaks Dam on the Santa Ana River, destroying significant least Bell's vireo habitat in the process.
1998 – A Center lawsuit secured protections for several of California's endangered species, including the least Bell's vireo, by forcing the U.S. Forest Service to amend its management plans for Southern California's four national forests.
March 2000 – The Center filed suit against the Bureau of Land Management for refusing to curtail overgrazing on 10.2 million acres of Southern California desert, thereby pushing the least Bell's vireo and 23 other endangered species toward extinction.
February 3, 2004 – The Center published a report illustrating how the 2003 Southern California wildfire season had significant impacts on habitat for imperiled wildlife, including the least Bell's vireo. The report called on federal and state wildlife agencies to consider these impacts before approving new development projects.
December 20, 2007 – The Center announced its intent to sue the Department of Energy over the designation of the Southwest National Interest Electric Transmission Corridor through least Bell's vireo habitat.
March 25, 2008 – The Army Corps revoked authorization to begin work on the Shadowrock luxury-home development in Chino Canyon. This action was taken in response to a lawsuit brought by the Center to protect important least Bell's vireo habitat.
April 2008 – The Center submitted comments on the Tehachapi Uplands Multi-species Habitat Conservation Plan being prepared by Tejon Ranch, which threatens harm to the least Bell's vireo through the ranch's development.
April 8, 2010 – The Center, San Bernardino Valley Audubon Society, Sierra Club, and Friends of Riverside's Hills filed suit challenging an industrial development planned within a wildlife area in the city of Riverside, including key habitat for the least Bell's vireo.
April 22, 2010 – As a result of a lawsuit by the Center for Biological Diversity and the San Bernardino Valley Audubon Society, a 1,100-acre wildlife preserve in western Riverside County was saved from industrial development. The preserve is home to numerous imperiled species, including the burrowing owl, least Bell's vireo, and southwestern willow flycatcher.
August 2, 2010 ? The Center sent a notice of intent to sue the U.S. Army Corps of Engineers over a new policy that would require stripping levees of vegetation that provides important habitat for imperiled California species, including the least Bell?s vireo and southwestern willow flycatcher.