Related Rule
Argentina
Practice Relating to Rule 18. Assessment of the Effects of Attacks
Argentina’s Law of War Manual (1989) states:
Those who plan or decide upon an attack shall, as far as possible, abstain from deciding to launch an attack … if it becomes apparent that the attack may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. 
Argentina, Leyes de Guerra, PC-08-01, Público, Edición 1989, Estado Mayor Conjunto de las Fuerzas Armadas, aprobado por Resolución No. 489/89 del Ministerio de Defensa, 23 April 1990, § 4.07(1).