In IHL, the principle of non-discrimination is reflected in rules prohibiting adverse distinction in treatment of persons based on criteria such as race, gender, nationality, religion or political affiliation. All protected persons – i.e., prisoners of war, civilian internees, the wounded and sick and others who are hors de combat should be treated with the same consideration by parties to the conflict. Each and every person affected by armed conflict is entitled to his/her fundamental rights and guarantees, without discrimination.
The only distinctions that are permitted in IHL may be referred to as favourable distinctions, such as, for example, triage of the wounded and sick based on the severity of their wounds, or those due to the different statuses IHL foresees (e.g. the difference between civilians and combatants or between protected civilians and civilians who do not have protected person status).
See Fundamental principles of IHL;
treatment without any adverse distinction
GCI, 12/2 (see ICRC updated Commentary)
GCII, 12/2 (see ICRC updated Commentary)