2000 – The Center and allies won a settlement placing 48,000 acres of the Algodones Dunes off limits to off-road vehicles; in another round of negotiations, the protection area was increased to 49,130 acres. In total, 81,550 acres, or 54 percent of the dunes area, were protected for Peirson's milk vetch and other imperiled desert species.
2003 – The U.S. Fish and Wildlife Service proposed that 52,780 acres of the Algodones Dunes be designated as critical habitat for the survival and recovery of the Peirson's milk vetch.
2004 – The Service designated only 21,800 acres of critical habitat for the milk vetch — an area nearly 60 percent smaller than the original proposal of 52,780 acres. The Service rejected a petition from the off-road industry to remove Endangered Species Act protection for the milk vetch, finding that the rare flowering plant is harmed by off-road use and needs ongoing legal protection.
September 28, 2006 – The Court ruled to uphold current protections for Algodones Dunes and its imperiled endemic species, reinforcing the supremacy of the Endangered Species Act over off-road recreational vehicle use.
July 27, 2007 – The Service issued a new critical habitat proposal for the federally and state-protected milk vetch. The new proposal identified only 16,108 acres of land in the Algodones Dunes as habitat necessary for the survival and recovery of the rare plant — a 25-percent reduction of currently protected critical habitat.
January 2008 – The Service published a final rule reducing the species' critical habitat to just 12,105 acres.
March 6, 2008 – The Center, Public Employees for Responsibility, Desert Survivors, and the Sierra Club filed notice of intent to sue the Fish and Wildlife Service for reductions in the Peirson's milk vetch's critical habitat.
July 17, 2008 – The Service dismissed a petition by off-road vehicle interest groups to remove the Peirson's milk vetch from the endangered species list, determining that the plant was still threatened with extinction by rampant off-road vehicle activities in its habitat.
January 14, 2009 – The Center filed suit against the Bush administration over its 2007 reduction of critical habitat for the Peirson's milk vetch.