text: Chapter 1
  status; in certain respects these classes are treated like combatants, but in other respects they are treated like
  civilians.
  CERTAIN HUMANITARIAN PERSONNEL
  1-60. Certain categories of medical and religious personnel, both members of the armed forces and civilians,
  have humanitarian duties that involve participation in hostilities (without committing acts harmful to the
  enemy), but also provide them with special protections:
  * Military medical and religious personnel (GWS art. 24, 33);
  * Authorized staff of voluntary aid societies (GWS art. 26);
  * Staff of a recognized aid society of a neutral country (GWS art. 27); and
  * Auxiliary medical personnel (GWS art. 25).
  CERTAIN CIVILIAN SUPPORTERS OF THE ARMED FORCES
  1-61. Certain categories of persons are not members of the armed forces and do not have combatant
  immunity, but are nonetheless authorized to support the armed forces in the fighting (see, for example,
  Department of Defense Instruction [DODI] 3020.41 [discussing contractors authorized to accompany the
  force]) and are entitled to POW status if captured during an international armed conflict:
  * Persons authorized to accompany the armed forces but who are not members thereof (GPW art.
  4A(4)); and
  * Members of the crews of merchant marine vessels or civil aircraft (GPW art. 4A(5)).
  UNPRIVILEGED BELLIGERENTS
  1-62. In addition to distinguishing between combatants and the civilian population, LOAC distinguishes
  between privileged and unprivileged belligerents. Persons who are not members of the armed forces as
  described in GPW (art. 4) but who engage in hostilities deprive themselves of many of the privileges attaching
  to the members of the civilian population. As the U.S. Supreme Court stated in Ex Parte Quirin, “Lawful
  combatants are subject to capture and detention as prisoners of war by opposing military forces. Unlawful
  combatants are likewise subject to capture and detention, but in addition they are subject to trial and
  punishment by military tribunals for acts which render their belligerency unlawful.” (317 U.S. 1 [1942])
  Unprivileged belligerents are persons who, by engaging in hostilities, have incurred the corresponding
  liabilities of combatant status (for example, being subject to attack or detention), but who are not
  entitled to the distinct privileges of combatant status (for example, combatant immunity and POW
  status upon capture).
  Unprivileged Belligerents as a Category in Treaty Law
  1-63. Although States have defined categories of lawful combatants in treaties (HR art. 1; GWS art. 13;
  GPW art. 4), States have seldom explicitly recognized in treaties, much less affirmatively defined, legal
  categories of unprivileged belligerents (see HR art. 29-31; GC art. 5; consider AP I art. 46). States have
  generally refrained from doing so because LOAC treaties have been understood to reflect restrictions on the
  conduct of hostilities by States, and States have been reluctant to agree to restrictions on their ability to
  respond to unprivileged enemy belligerents, or to afford such persons the distinct privileges afforded civilians
  or lawful combatants. Thus, the concept of unprivileged belligerency has primarily been understood in
  opposition to the rights, duties, and liabilities of lawful combatants and civilians, and as a necessary
  implication of creating these two latter legal categories (see, for example, 10 U.S.C. § 948a). Unprivileged
  belligerents have been viewed either as combatants who have forfeited the privileges of combatant status by
  engaging in spying or sabotage, or as civilians who have forfeited certain protections of civilian status by
  joining armed groups that fail to qualify as lawful combatants or by otherwise engaging in acts of hostility
  against the opposing armed forces.