 A trademark dispute involving the owners of the identically named Burger King in Mattoon , Illinois led to a federal lawsuit ; the case 's outcome helped define the scope of the Lanham act and trademark law in the United States . An existing trademark held by a shop of the same name in South Australia forced the company to change its name in Australia , while another state trademark in Texas forced the company to abandon its signature product , the Whopper , in several counties around San Antonio . Legal decisions from other suits have set contractual law precedents in regards to long @-@ arm statutes , the limitations of franchise agreements , and ethical business practices ; many of these decisions have helped define general business dealings that continue to shape the entire marketplace . 
