That the second scenario is more frequently encountered in practice suggests that an analysis of the legal implications is more pressing. Both situations raise interesting legal issues, however the second scenario, given the greater frequency, raises them more often. We will proceed on the assumption that State B (for example Russia) intervenes against rebels (Chechens) on the territory of State A (Georgia), without Georgia's consent or involvement.
We will consider a number of different permutations of the available facts and their concomitant legal implications, both in terms of Ius ad Bellum and Ius in Bello. We will firstly consider whether an international armed conflict exists, and between whom. We will then move on to consider the trigger factors for the conflict, as this will determine the legality of the recourse to the use of force. This is linked to considerations of the attribution of the acts of non-state actors to states that harbour them, which in turn raises questions about the factual relationship between State A and the rebels. The final factual permutation relates to the origin of the rebels. We will then proceed to consider over-arching legal regimes, such as Human Rights obligations and pre-existing bi- and multi-lateral treaties.
It could be seen as peculiar that, in none of the laws that codify armed conflicts, a definition of armed conflict itself has been given. This definition is vital: only from the moment that an armed conflict exists, IHL can be applied. As Pictet described in his commentaries on common article 2 of the Geneva Conventions (GC), it is sufficient that hostilities exist de facto. The applicability of the Geneva Conventions does not need the declaration of war, nor the recognition of a state of war. In paragraph 70 of the Tadić case (Prosecutor v Tadić  35 ILM 35), the International Tribunal for the Former Yugoslavia finds that 'an armed conflict exists whenever there is a resort to … protracted armed violence between governmental authorities (of State B) and organised armed groups (the rebels on the territory of State A)'. It therefore becomes necessary to consider both the extent and duration of the military operations. If the intervention is on a small scale for a very limited period of time, it seems unlikely to reach this threshold. On the other hand, a massive intervention by large numbers of troops over a long period of time will more obviously meet this criterion.
The Conventions are primarily made to protect individuals and not the interests of States; the Roman law maxim mirrors this hominum causa omne ius constitutum est.
Assuming that State A is engaged in hostilities against rebels on its territory, the law applicable would be that of a non-international armed conflict. This would therefore be Additional Protocol-II and common Art. 3 of the Geneva Conventions. Additionally, domestic legislation (most importantly criminal provisions) remains applicable, unless international law over-rules it. Whilst this would provide some protection, the full conventions would apply far more comprehensive and clear protection.
The remainder of this essay will consider the situation where State B is involved in hostilities against the rebels.
If State B's intervention was the first act of violence, then it can either be regarded as anticipatory selfdefence, or armed aggression. The Caroline case (The Caroline Case, 30 BFSP 195-6 ) illustrates an early example of pre-emptive self-defence. This precedent, however, has become obsolete in the light of changing state practice. The very signing of the UN Charter evidences this change.
The accepted nature of self-defence would not seem to include pre-emptive action, as such action would be incompatible with the text of Art. 51 UN Charter. As this article provides an exception to the general principle of pacific dispute resolution and collective security (which is the purpose of the UN Charter), it must necessarily be interpreted narrowly. As a consequence, the right of anticipatory self-defence does not have an explicit legal basis. Indeed, previous similar interventions have been condemned by the UN Security Council, such as Israel's attack on an Iraqi nuclear installation in 1981. The most recent Iraq conflict could well act as a catalyst to change this position when taken in to consideration with 9/11.
The legal basis for such a condemnation can be seen in Art. 2 UN Charter, as affirmed by the ICJ in paragraph 212 of the Nicaragua case: states are obligated to respect the territorial integrity and political sovereignty of other states. Thus whilst an intervention against a non-state actor on the territory of another state may or may not violate the principle of political sovereignty, it certainly violates territorial integrity and perhaps even their neutrality
Whilst anticipatory self-defence has at best a dubious legal basis, unjustified armed aggression remains contrary to the purposes of the United Nations, and as such is illegal.
Certain other provisions in the UN Charter contain exceptions to this principle, such as the inherent right of individual or collective self-defence under Art. 51 UN Charter. This article would be applicable to State B if the rebels attacked State B first, prior to any form of intervention. It would also apply to State A, given that a violation of its territory has taken place. On the other hand, had the rebels not first attacked State B, State B might still have some right of recourse to force in the context of a punitive measure, provided that their was some initial insult or breach of international law that needed to be 'avenged'.
If one can claim the right of self-defence against non-state actors, State B's response is legitimate. They have been attacked, and are now resorting to force of arms to redress this injury. On the other hand, if such a right does not exist, State B's actions are equivalent to either anticipatory self-defence, or even simple armed aggression.
We submit that such non-state actors as rebels and terrorists may well have sufficient legal personality to be the object of self-defence, but should not simply because of this benefit from combatant status. They should be required to demonstrate sufficient discrimination in terms of Art. 43 AP-I.
The fact that the rebels are a non-state actor is not necessarily a bar for them to declare themselves bound by various treaties; the Palestinian Liberation Organisation has unilaterally done so with AP-I.
The command-authority necessary to create such a relationship of attribution is either 'effective' (Nicaragua) or 'overall' (Tadić). Effective suggests a tighter degree of control than does overall. The International Law Commission returns to the Nicaragua judgement in its formulation of State Responsibilities. Recent legal discourse, subsequent to 9/11, suggests a more expansive view.
If such attribute can take place, then the conflict is of necessity an international one. This will mean that the complete spectrum of IHL instruments will apply (depending on ratification of certain of the non-customary laws).
The other possibility is that they are originally from State B. This could perhaps turn the substance of the conflict into a non-international one. The only international aspect of this conflict would be the location, and David suggests that merely one foreign element is not sufficient to render a conflict international. This seems doubtful, however, given that territory is a very substantial and politically charged element. Should the conflict be non-international, then AP-II would become applicable, provided that State B has ratified it, and the conditions of Art. 1 AP-II are fulfilled. It is important also to stress that common article 3 of the Geneva Conventions would apply.
On the other hand, State A may be unable to directly fight against the rebels, but is at the same time hostile to foreign intervention. An historical example might be Turkish offensives against Kurds in northern Iraq. The Iraqi government was unwilling to see foreign forces on its territory, but was restricted in what military operations it could mount against the Kurds themselves.
This distinction would make little difference in terms of the IHL, but would be of importance in terms of ius ad bellum.
In principle, human rights law is always applicable. But some human rights may be derogated from in "times of national emergency which threatens the life of the nation and the existence of which is officially proclaimed" (e.g. Art. 4 ICCPR, reaffirmed by the ICJ in its Nuclear Weapons Advisory Opinion). Only a core of non-derogable human rights such as the prohibition of slavery and the prohibition of torture and inhumane treatment would still apply in such a situation.
The Right to Life is also regarded as non-derogable right, but it must be seen in the context of IHL. Thus it becomes somewhat devalued in a regime that permits not only the killing and injury of combatants, but also collateral damage to civilians.
Thus State B could declare such an emergency, but only after having informed the other States Parties about the provisions from which it has derogated, and only on a temporary basis (UN Human Rights Committee General Comment No. 29).
Moreover, in many situations of armed conflict, it is not the government but a non-governmental entity that exercises control over people, and these entities usually deny that they are bound by international standards like Human Rights Covenants. [a bit inconsistent with PLO thing, no?] That could be the case with the rebels on the territory of State A. As a consequence, significant gaps in human rights' protection still remain.
We qualify this conflict as international for a number of reasons. Firstly, given the attitude of the Georgian authorities (and their unwillingness or inability to deal with the Chechen insurgents), this will justify a punitive reprisal by Russian forces. The conflict therefore becomes international in scope. Given the history of conflict between the Russians and the Chechens, the attack can be seen as either an instance of anticipatory selfdefence (in which case it would probably currently be illegal), or simply the continuation of existing hostilities on another front. In this second case, Russia is in violation of Georgia's territorial sovereignty. Both of these are Ius ad Bellum considerations; they will not change the applicable law during the actual conduct of hostilities.
The origin of rebels, despite them being nominally nationals of the Russian Federation, does not outweigh the other factors described above. The conflict therefore remains international.
As an international armed conflict, the law applicable in terms of IHL will be the Hague-law and the Geneva Conventions. AP-I will also apply as both countries have ratified it. This will insure that at least a minimum standard of military conduct is obeyed, and that, where it is not obeyed, offenders will be punished. By preserving this element of humanity in the very heart of armed conflict, International Humanitarian Law keeps open the path towards reconciliation and contributes not only to restoring peace among the belligerents but also to fostering harmony amongst peoples.