Editor’s Note: This article is part of the Armed Groups and International Law Symposium, building on the volume edited by  and .

During international armed conflicts, combatants (i.e., members of the armed forces of a party to the conflict) have the right to directly participate in hostilities. In case of any alleged wrongdoing, the so-called “combatant privilege” applies both before domestic and international criminal courts and tribunals. As a result, combatants cannot be prosecuted for their mere participation in the fighting, so long as they act in accordance with international humanitarian law (IHL) (see generally Ohlin). However, those fighting on behalf of non-state parties to a non-international armed conflict (NIAC) do not enjoy such immunity from criminal prosecution by virtue of IHL. This distinction, or rather imbalance, has led to calls for belligerent equality for the parties to NIACs, and to start offering combatant immunity to members of non-state armed groups to enhance compliance with IHL (see, e.g., Gill, Corn, and Cassese).

This is nevertheless unacceptable for States. State practice shows a refusal to accept members of armed groups opposing the government as persons who may lawfully take part in belligerent acts, except in the specific (and very limited) situations listed in Article 1(4) of Additional Protocol I to the Geneva Conventions (that is, “fighting against colonial domination and alien occupation and against racist regimes in the exercise of their right of self-determination,” see, e.g., Fortin). States are resolved to preserve the prerogative to treat rebels as unprivileged belligerents who unlawfully (under domestic law) participate in hostilities, maintaining the difference between State-sanctioned participation in warfare and any unsanctioned participation.

The lack of combatant privilege results in a concomitant lack of “combatant immunity” for members of armed groups in case of domestic prosecution for otherwise lawful belligerent acts. Domestic criminal trials therefore treat members of non-State actors differently than members of State armed forces – including when the former do comply with IHL. A similar unequal treatment is not apparent at the international level, where members of governmental armed forces and members of these groups are treated alike. What is lawful or unlawful for a State combatant under IHL is also considered lawful or unlawful for a member of an armed group. As explained in my chapter in the book that is the subject of the present symposium, due to the jurisdiction of international criminal courts and tribunals being limited to, inter alia, war crimes and crimes against humanity, and because these courts and tribunals treat all of IHL (for IACs as well as NIACs) as legitimizing certain otherwise unlawful conduct (such as killing and destruction), members of organized armed groups are effectively afforded a form of combatant immunity in those forums.

In the book, I also make some proposals for international criminal law, but here I focus on the treatment of members of armed groups in domestic courts, and will argue that recognizing some form of “combatant” (or rather: fighter) immunity with respect to IHL-compliant activity in NIACs would be opportune, especially in relation to conduct occurring outside of the prosecuting State.

Domestic prosecutions for conduct during non-international armed conflict

In NIACs, any killing of a government soldier or destruction of governmental military facilities by an armed group member (or anyone else) would, unless done as proportionate personal self-defense, violate domestic laws even when not in violation of IHL. IHL does not prohibit such conduct, but it does not explicitly authorize it during such conflicts either. Moreover, IHL applicable to NIACs does not provide an excuse or defense under criminal law for the killing of those participating in hostilities and/or destruction of military objectives.

Members of armed groups do not have combatant immunity under domestic law. As an armed rebellion against the government is the archetype of treason, this seems obvious for trial against those who opposed the government of the State where they are being prosecuted. Yet, the lack of combatant immunity appears to be the same when a member of an armed opposition group fought in another country and/or against another government, or did not try to impede on the territorial integrity of the State where he or she is prosecuted.

The Supreme Court of the United Kingdom held that international law does not prohibit the domestic criminalization as terrorism of hostile acts during NIACs, even when it concerns targeting of military objectives. In R v Gul, it noted “that insurgents in non-international armed conflicts do not enjoy combatant immunity” (para. 50). This observation is, of course, correct. Although IHL does not prohibit taking an active part in hostilities, it does not positively authorize it. Conduct that is not prohibited under IHL can therefore still be prosecuted as a domestic crime.

What is more problematic are findings, such as those in the case against Omar Khadr, where conduct that was not prohibited under IHL but allegedly carried out by members of armed groups, is prosecuted as a violation of IHL (rather than domestic law). Before the military commission set up by the United States for those individuals held in Guantanamo Bay, Mr. Khadr, was charged and subsequently pleaded guilty to, inter alia, crimes referred to as murder and attempted murder “in violation of the laws of war,” even though it concerned the throwing of a grenade at a U.S. soldiers in the middle of a battle.

In a case concerning alleged “terrorists” who fought in the Syrian Civil War, a magistrate judge of the U.S. District Court in Missouri did consider, in an interesting opinion, that as a result of the U.S. recognition of belligerency of the Syrian opposition (i.e. the Free Syrian Army), the conflict was “factually analogous to [NIACs] in which the United States recognized lawful combatant immunity for participating forces, especially civil wars” (see here). The judge therefore recommended “that defendants be permitted to submit the lawful combatant immunity affirmative defense at trial.” However, as is clear from the opinion issued by the District Court overturning that opinion, and the U.S. case law she refers to, the magistrate’s view was an outlier. This later judge “conclude[d] that the defendants in this case are not entitled to combatant immunity. Their assertion of this defense fails, and they may not assert it as a defense at trial” (here).

In 2011, in what appears to be a similar outlier judgment, the District Court of The Hague (The Netherlands), in a case concerning alleged financing of and support for terrorism and war crimes committed in Sri Lanka by the Liberation Tigers of Tamil Eelam (LTTE) during the Sri Lankan Civil War, ruled that the accused could not be prosecuted for part of the alleged crimes because the conduct was governed by IHL. However, this finding was reversed by the Appeals Court of The Hague, which found that contrary to combatants in an international armed conflict, members of armed groups who participate in a NIAC “without combatant status” are “unprivileged” belligerents and may be prosecuted under domestic criminal law (see Consideration Called upon to address the matter, the Dutch Supreme Court recalled a finding it had previously made as part of extradition proceedings sought by Turkey concerning an alleged member of the Kurdistan Workers’ Party (PKK), when it had ruled that IHL does not provide a defense in domestic criminal trials when it concerns fighting as part of a NIAC. According to the Supreme Court,

Common article 3 of the Geneva Conventions prohibits – in summary, in so far as is relevant for these purposes – any party involved in an armed conflict not of an international character (hereinafter: ‘an internal armed conflict’) from committing violence to the life or person of anyone who is not taking part or has ceased to take part in the hostilities. […] It does not follow from the nature of article 3 that persons other than those not participating in the conflict are not entitled to protection against violence against their life or person. This article does not legitimize such acts. The view that in the case of an internal armed conflict international humanitarian law applies exclusively and general criminal law is therefore inapplicable is incorrect.

This approach has persisted in Dutch trials. In 2014, a Dutch so-called “foreign fighter,” who had travelled to Syria to join a jihadist group called al-Jabhat al-Islamiyyah, was convicted for, amongst other crimes, attempted murder. When considering the accused’s defense that his acts were lawful acts of war, the judges noted that as a member of an organized armed group fighting in a NIAC, he did not have a combatant privilege. As such, the Court held, he did not enjoy immunity from prosecution for his participation in hostilities. Consequently, it was not considered whether the accused directed his acts at legitimate military targets or only at protected persons or objects.

Not only alleged members of terrorist organizations were treated in this way. In 2016, a former member of the Dutch special forces who had travelled to Syria to join the YPG, a Kurdish armed group supported by the Dutch government (and a broader multilateral coalition) in their fight against ISIS, was arrested for allegedly killing, as a sniper, members of ISIS. The Dutch prosecution services stressed that the suspect’s acts could qualify as murder under Dutch criminal law, notwithstanding the existence of a NIAC and the persons killed being members of an organized armed group. It appears, therefore, that the presumption that violence during armed conflicts was directed at legitimate targets and the onus to prove otherwise, as it applies during international criminal trials (see, e.g., Ntaganda Trial Judgment, at paras 886 and 925), is not recognized in the same way on the domestic level.

Belgian courts have been rather ambiguous in their approach to this issue. In recent years, a number of criminal cases dealt with “foreign fighters” who have travelled to Syria or elsewhere to join or otherwise support groups fighting against a government or other armed groups (see here and here for a discussion of some of these cases). Since Article 141bis of the Belgian Criminal Code excludes “acts of armed forces during an armed conflict” from the application of Belgian criminal law, the Belgian courts had to consider whether specific groups in Syria that qualified as terrorist groups under Belgian law at the same time qualified as such “armed forces.”

Due to the phrasing of the exclusion clause, which of course should have referred to acts in accordance with IHL or lawful belligerent acts, members of organized armed groups could invoke this clause to argue a kind of combatant immunity as a defense. In response, Belgian courts, rather counter-intuitively, found that well-organized groups, such as Al-Nusra but also ISIS, did not constitute organized armed groups under IHL (see here for an overview). The persons alleged to have belonged to these groups therefore could not rely upon the exclusion clause. In another case, the Brussels Court of Appeal did consider that a lower judge had correctly found that the PKK and Turkey were involved in a NIAC, and the exclusion clause therefore applied to the conduct of the alleged PKK members. It seems, however, to apply to all their acts committed during the armed conflict – also those contrary to IHL.

A form of immunity in domestic courts for IHL-compliant activity in NIACs

The foregoing shows that domestic proceedings have a very different approach to international criminal law, in that they tend to reject the idea that the lawfulness of certain conduct under IHL must be taken into consideration when addressing alleged acts by members of non-State organized armed groups.

Historically, the ability to criminalize hostile acts by armed groups (whether opposing the government or fighting each other on the territory of a State) followed from prescriptive territorial criminal jurisdiction. As NIACs were initially purely seen as classic civil wars, whereby an organized rebel force fought against the government of a State, the very taking up of arms against the State logically was in violation of domestic laws. Fighting between armed groups without the involvement of the armed forces of the State remained solely within the prerogative of States, as a matter of internal sovereignty (see here), until the International Criminal Tribunal for the former Yugoslavia, in Tadić, expanded the notion of NIAC to include the “resort to armed force between [organized armed] groups within a State.” (para. 70)

Whenever States allowed sovereignty to make way for IHL to become applicable to NIACs, States always wished to be able to criminalize any hostilities within their own borders, even if the acts were in line with IHL. International criminal jurisdiction, or jurisdiction over alleged war crimes committed elsewhere (i.e., on the territory of another State or the High Seas), only arose if the rules of IHL were violated. Nowadays, however, the expansion of counter-terrorism regulation has resulted in the “expansive territorial criminalization” of conduct by members of parties to NIACs by States other than the State on whose territory the fighting takes place (Saul, p. 419).

Although the prosecution of war crimes, including those committed during NIACs, generally reinforces and indeed complements IHL’s protective scope, thereby assisting in limiting suffering during armed conflicts, the approach by domestic courts described above risks interfering with IHL’s regulation of violence. This is especially so when acts by members of alleged terrorist organizations are codified as crimes under domestic criminal law by reference to the prohibition of terrorism or the lack of combatant immunity for NIACs, whilst the conduct is not unlawful under IHL. In this regard, it is worth noting that many armed groups are designated as terrorist organizations for political reasons. The aforementioned approach therefore risks undermining the – already limited – incentives for members of organized armed groups to respect IHL.

It is understandable that governments fighting armed opposition groups are unwilling to grant a NIAC version of combatant immunity to their opponents, unless this follows from a peace agreement such as the one in Colombia. Yet, it would be helpful to the promotion of IHL-compliance if domestic criminal trials of persons who have fought in NIACs elsewhere, i.e., not in the country where the prosecution takes place, would recognize some form of immunity for the conduct of hostilities acts that did not violate IHL applicable to NIACs.

Image:  Fighters from the Free Syrian Army cheer and react as they fight against the Islamic State (IS) group jihadists on the outskirts of the northern Syrian town of Dabiq, on October 15, 2016. (Photo by Nazeer al-Khatib/AFP via Getty Images)