A quick comment about status under GCIII, Art. 4, which defines persons who qualify as POWs. (I've posted part of this as a comment at National Security Advisors, too.)
There is seemingly an irreducible "group" element to Article 4(A)(2). It says that a person qualifies as a POW if he is a member of a militia or volunteer corps, provided that the militia or volunteer corps (that is, the group, not merely the individual) fulfils certain criteria.
Why the group element of the definition? What might be the rationale? The group element, considered at the most general level, deliberately rules out 'armies-of-one'. Why? Presumably as being inherently undisciplined because there is no command structure to them. Hence the requirement for commanders, group structure, someone to take responsibility for adherence to the rules of war, etc.
I have always read that to mean that - and I've always thought that the ICRC agreed - that this meant that the group must satisfy these criteria in order for any particular individual to benefit from POW protection under them. The incentive rationale for this is that much greater incentives are provided to members of armed groups to follow the war rules if there is the possibility of membership-status liability on account of the group itself even if you yourself have not individually committed any further war crime.
Thus it would be possible for an individual member to be part of a group that flunks these criteria, and so be liable as an unlawful combatant
- (i) if the group fails these tests,
- (ii) the individual is a member, and
- (iii) even though the individual may not have individually engaged in separate war crimes as part of the group. That is, the individual is chargeable as a member with unlawful belligerency in an article 2 conflict. The member is not chargeable with specific war crimes in which he did not participate - leaving aside special questions of conspiracy, aiding and abetting, etc. - but he is chargeable with the underlying status crime.
Although I've never seen any real discussion on it and not sure if there is much, the language in this section refers not to combatants, but to "members." It is arguably the case that this is a broader category that "combatant," in the formal sense of someone who takes 'active [or direct] part in hostilities'. Meaning that potentially one could be a member without having taken active part in hostilities, but still be liable as an unlawful belligerent. One could also argue, on the other hand, that 'members' here is intended to be a subset of combatants.
The first part of this post about group requirements I've long understood to be the standard view pretty plainly expressed in article 4, but maybe I've long missed something. I'd welcome any thoughts, particularly on that last point, on which I've never read commentary.
(I would also add, as a side note, that the military forces in internal armed conflicts I've monitored, especially, tended to fall into two categories, whether regular government forces or insurgents. On the one hand, you had highly disciplined forces, in the general sense, who nonetheless systematically violated the laws of war because they had been trained to fight in ways that were violative of the law - their commanders had simply decided to ignore the legalities and had trained their forces accordingly. On the other hand, you had utterly undisciplined forces in which violating the laws of war - rape, pillage, murder, generally trashing the places they went - was simply part and parcel of the general indiscipline of the forces, and usually the lack of an NCO cadre. So, for example, the Georgian forces, trying ineffectually to hold Sukhumi in 1993 against the Abkhaz insurgents, were so undisciplined in everything that they spent their time in the city ransacking the place and doing a lot of drugs and drinking, instead of digging fortifications and getting ready for the assault, which took them mostly by surprise. And then there is the Guatemalan army strategy in the early 1980s, which more or less combined the two - an otherwise highly disciplined army (at that time) relied upon being able to turn on and off its soldiers to go crazy and sack a village, and then return to discipline.)