The cornerstone principle of IHL is that of distinction which all parties to a conflict must abide by at all times, namely to “distinguish between the civilian population and combatants and between civilian objects and military objectives and accordingly [to] direct their operations only against military objectives” (article 48 Additional Protocol I). This means that there must be clear definitional boundaries between the “civilian population” (who are protected persons and may never be deliberately targeted unless they change status to combatants/take up arms, see, e.g., article 50(1) Additional Protocol I), and “combatants” (who may be deliberately targeted). The correct classification is important since, in situations of IAC, under Geneva III combatants are entitled to protection as prisoners of war following capture; and “can be prosecuted only for violations of international humanitarian law, in particular for war crimes” (article 43(2) Additional Protocol I). Though States did not agree to extend such combatants’ privileges in NIACs to members of organized armed groups or civilians directly participating in hostilities, they may elect to treat captured fighters as prisoners of war as a matter of policy. (Especially helpful in the drafting of this section was Malzer, 2016, and Pejic, 2012, Ch. 7).

This section gives an overview of the rules governing the classification of combatants (international armed conflicts – IAC) and fighters (non-international armed conflicts – NIAC) and identifies some of the key areas of contention that have surrounded the classification of non-State terrorist actors such as al Qaeda and ISIL.