Соответствующая норма
Peru
Practice Relating to Rule 145. Reprisals
Section B. Reasonable notice and measure of last resort
Peru’s IHL Manual (2004) states:
(3) Reprisals may only be taken as a last resort to enforce international humanitarian law and make the enemy comply with its provisions.
(4) A formal warning must be given to the enemy, notifying it of the action that will be taken if it continues to commit or repeats its violations of international humanitarian law. 
Peru, Manual de Derecho Internacional Humanitario para las Fuerzas Armadas, Resolución Ministerial Nº 1394-2004-DE/CCFFAA/CDIH-FFAA, Lima, 1 December 2004, § 25.c.(3) and (4).
Peru’s IHL and Human Rights Manual (2010) states:
(3) Reprisals may only be taken as a last resort to enforce international humanitarian law and make the enemy comply with its provisions.
(4) A formal warning must be given to the enemy, notifying it of the action that will be taken if it continues to commit or repeats its violations of international humanitarian law. 
Peru, Manual de Derecho Internacional Humanitario y Derechos Humanos para las Fuerzas Armadas, Resolución Ministerial No. 049-2010/DE/VPD, Lima, 21 May 2010, § 29(c)(3)–(4), p. 234.