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Mexico
Practice relating to Rule 66. Non-Hostile Contacts between the Parties to the Conflict
Section B. Use of the white flag of truce
Mexico’s Army and Air Force Manual (2009), in a section on “Distinctive signs”, states that the “white flag … [is] used for negotiation”. 
Mexico, Manual de Derecho Internacional Humanitario para el Ejército y la Fuerza Área Mexicanos, Ministry of National Defence, June 2009, p. 143.