Prior to Argentina's friendly clash with Slovenia in La Plata on June 7, which they won 2-0, the South American players stood behind a banner relating to the ownership of the islands.
The Falklands have been ruled by the United Kingdom since 1833 but due to their location in the southern Atlantic Ocean, Argentina maintain their claim on the archipelago.
The banner read Los Malvinas son Argentinas (The Falklands are Argentinian) which FIFA deemed to break two articles of their code of conduct, and issued a fine of CHF 30,000 as well as the warning.
In a statement, FIFA confirmed the AFA were in breach of article 60 of the FIFA Stadium Safety and Security Regulations ("Political action") that states the promotion of political or religious messages inside or close to a stadium is "strictly prohibited" before, during and after matches.
FIFA also announced the banner and actions of the players had also broke article 52 of the FIFA Disciplinary Code ("Team misconduct") that explains action will be taking where a team "fails to conduct itself properly."