They were invaded in 1982 under orders from Argentina's then-military dictatorship, triggering a 10-week war won by Britain."The World Cup might not be ours, but the Falkland Islands definitely are," a spokesperson for Prime Minister Keir Starmer said."Self-determination rests with the islanders, and our commitment to the Falklands will never waver."Sir Keir supported calls for FIFA to investigate, the spokesperson said, after UK Business Secretary Peter Kyle said the players' behaviour was "entirely inappropriate."FIFA can prosecute Argentina's players and soccer federation because its disciplinary code prohibits, at stadiums, any "message that is not appropriate for a sports event," including those of "a political, ideological, religious or offensive nature".The FIFA fines for political messaging range from around $US5,000 to $20,000 ($AU7,100 to $28,500) Argentina plays Spain in East Rutherford, New Jersey.Argentina players displayed the same "Las Malvinas son Argentinas" slogan during a warm-up game in Buenos Aires in June 2014, ahead of the World Cup that started days later in Brazil.FIFA's disciplinary panel ruling in that case was published after the tournament finished and fined the Argentina federation $37,000.In the 2012 London Olympics case, FIFA's ruling said the conduct of the South Korea player "cannot be tolerated."At the 2022 World Cup, FIFA fined the Serbian federation $24,800 for hanging a political banner about neighbouring independent state Kosovo in the locker room before playing Brazil.It showed a map of Serbia that included the territory of Kosovo, which has been an independent state since 2008, and the slogan "No Surrender."AP