Соответствующая норма
Practice Relating to Rule 106. Conditions for Prisoner-of-War Status
Section C. Situations where combatants cannot distinguish themselves
Croatia’s LOAC Compendium (1991) states that combatants must carry their arms openly “at least during every military engagement [and] as long as they are visible to the enemy while engaged in a military deployment”. 
Croatia, Compendium “Law of Armed Conflicts”, Republic of Croatia, Ministry of Defence, 1991, p. 6.