While sympathetic to American filibusters in Central America, he was instrumental in having Commodore Hiram Paulding removed from command for his landing of Marines in Nicaragua and compelling the extradition of William Walker to the United States. Cass attempted to buy more land from Mexico, but faced opposition from both Mexico and congressional leaders. He also negotiated a final settlement to the Clayton–Bulwer Treaty, limiting U.S. and British control of Latin American countries. The chiefs of Raiatea and Tahaa in the South Pacific, refusing to accept the rule of King Tamatoa V, unsuccessfully petitioned the United States to accept the islands under a protectorate in June 1858.