Foreign fighters from the UK asked to be identified as "Scouser", "Jacks" and "Ben Grant" pose for a picture as they are ready to depart towards the front line in the east of Ukraine following the Russian invasion, at the main train station in Lviv, Ukraine, 5 March 2022. REUTERS/Kai Pfaffenbach

Recent cases have highlighted the ongoing conundrum regarding the legal status of foreign fighters. Global Insight considers the issues.

In 2018 Aidan James, a British citizen, was charged with terrorism offences after returning home from the Middle East. James had joined a Kurdish group fighting in Syria against Islamic State (ISIS, also known as Daesh) and wrote in his diary that ‘Daesh is the biggest threat the world has seen since Hitler so anything I can do in these operations is good’. Yet, regardless of his motivation, James had become a ‘foreign fighter’ and the UK Attorney General approved his prosecution even though charges were not pursued against other British citizens in similar circumstances.

Two of the terrorism charges against James were dismissed. The judge noted: ‘You did this because you believed that you should stand up against ISIS and defeat them, both to help the Kurds and also to protect the population of the United Kingdom against terrorist attacks inspired by ISIS here.’ Nevertheless, James was convicted on a narrower charge of attending a place used for terrorist training by the PKK (or Kurdistan Workers’ Party), an organisation proscribed by the UK. The organisation he actually fought with was another Kurdish group, the YPG (or People’s Defense Units), which the judge hearing his case observed ‘was supporting the policy of the United Kingdom and other allies by fighting ISIS’.

Lawyers for another YPG fighter, James Matthews, who was charged more than two years after fighting in Syria, suggested that calculations had changed as the YPG had, by then, all but defeated ISIS and it was possible that the potential impact on relations with Turkey might be influencing the decision to bring an otherwise implausible prosecution. Terrorism charges were eventually dropped against Matthews.

Foreign fighters, an old profession

So, what is a ‘foreign fighter’ and why are there discrepancies in how they are treated, nationally and internationally? It is a longstanding question, but one which has become increasingly pertinent since the turn of the century as major conflicts burgeon around the world, notably in Syria and Ukraine, and most recently in Gaza.

Sara Elizabeth Dill is Treasurer of the IBA War Crimes Committee. ‘Foreign fighters, although a centuries old concept, do not have clear definitions under international law’, she says. ‘Many states have laws criminalising citizens joining a foreign military, and some allow this if the army they are joining is at peace with the home country. However, under some of these laws, whilst enlistment or foreign military service may be lawful, individuals could still face prosecution under terrorism laws.’

In earlier centuries, the actions of men and women who chose to fight abroad might never have been known or challenged in their homelands. But the rise of the nation-state, and the concept of national sovereignty within defined territorial boundaries, signalled a change. As early as the late 18th century states began to dictate when and where their citizens could fight, and against whom.

Early laws, such as the US Neutrality Act of 1794 and the UK’s Foreign Enlistment Act of 1870, were mainly aimed at preventing citizens fighting against their state’s recognised allies (or those that they are not at war with). ‘National laws against foreign fighting date back to the United States in the 1790s, but they are applied inconsistently’, says David Malet, Professor of Justice, Law and Criminology at the American University School of Public Affairs. ‘Governments will sometimes look the other way and permit their citizens to slip away for favoured causes, and some will even offer open support for popular causes, such as Ukraine.’ This can include national laws being contradicted by political statements, such as in February 2022 when UK Foreign Secretary (later Prime Minister) Liz Truss said she would ‘absolutely’ support British citizens who wanted to fight for Ukraine against Russia, although the British government subsequently affirmed that this would be illegal.

As national laws evolved, international laws were also being formulated on how states would conduct affairs between themselves in the event of conflict, and the status of foreign fighters inevitably came under consideration – notably in the 1977 Additional Protocol I (API) to the Geneva Conventions, which deals in part with mercenaries. The results, though, have been limited and inconclusive.

Terrorists and foreign fighters, says who?

In 2014, in an attempt to refine the definition of ‘foreign fighter’, the United Nations coined the term ‘foreign terrorist fighter’ in Security Council Resolution 2178. However, the resolution’s limited ambit added little clarity. As Malet explains, the resolution ‘required all member states to prevent their citizens from becoming “foreign terrorist fighters” (FTF) and to repatriate and prosecute any who do. However, FTFs were defined specifically as individuals crossing international lines to join affiliates of al Qaeda or the Islamic State. A person would not qualify as a FTF if they traveled to join a different jihadist group, let alone went to Ukraine or another conflict.’

Although certain organisations are proscribed as terrorist, either by the UN Security Council (UNSC) or by national governments, there is not necessarily consistent agreement. For example, Hamas is not designated a terrorist organisation by the UNSC, though it is considered as such by the EU, the US and several other countries. The Russian Wagner Group, which fought in Syria and is fighting in the war against Ukraine, is frequently described by the media as a mercenary organisation. But, as Dill notes, ‘Wagner’s status is a curious one, as the US only designated them as a transnational criminal organisation, whilst the UK went a step further and imposed the terrorist designation (which I find problematic)’.

International law offers little more clarity than national laws when it comes to identifying another type of foreign fighter, the mercenary. International humanitarian law (IHL) has tried to distinguish between a mercenary, namely someone who is motivated to fight essentially ‘by the desire for private gain’, and other foreign fighters. Article 47 of API (which applies to international armed conflicts only), establishes a narrow definition of a mercenary which is hard to apply. The article lists six cumulative conditions to be met for a person to be a considered a mercenary, prompting one academic commentator, Professor Geoffrey Best (author of Humanity in Warfare: The Modern History of the International Law of Armed Conflict), to remark that ‘any mercenary who cannot exclude himself from this definition deserves to be shot – and his lawyer with him’!

Dill illustrates the problem in relation to the Wagner Group: ‘It is unlikely that Wagner Group members would meet all of the definitions of a mercenary in the war in Ukraine, notably because of the element that they [mercenaries] can neither be a national of a party to the conflict nor a resident of territory controlled by a party to the conflict.’ In any event, the consequences of being defined as a mercenary under this definition are minimal, limited to the loss of prisoner of war status – and even then basic Geneva Convention protections regarding treatment and judicial guarantees remain.

So IHL does not forbid mercenarism or make it criminal. This creates yet another anomaly because some countries, like France, do prohibit and criminalise mercenarism. Two international conventions have also criminalised mercenarism in armed conflicts: the 1989 UN Convention against the Recruitment, Use, Financing and Training of Mercenaries and the 1977 Organisation of African Unity Convention for the Elimination of Mercenarism in Africa. However, the former has attracted only 37 states parties, excluding most European countries and the US, and the latter has just 32 signatories. States were also notably unable to agree a definition of mercenarism as a war crime for inclusion in the Rome Statue of the International Criminal Court (ICC). This limited support suggests either that there is scant agreement on the subject within the international community or that states prefer to retain sovereign influence over the issue, judging that the occasional utility of mercenarism is worth the chaos it can cause.

Indirect approaches to foreign fighters

Given the political and legal ambiguity attached to foreign fighters, individual states have frequently resorted to indirect means to address the problem, as Frank Rosenblatt, Professor at the Mississippi College School of Law, notes of the US government: ‘What we often see is that those who fight for less politically favoured causes will not be prosecuted for that affiliation per se, but are likely to draw the scrutiny of government investigators for other violations, such as immigration and customs violations.’ Malet agrees this approach is often used because ‘it is much easier for governments to try offenders for different charges like material support for a terrorist organisation, or simply being physically present in a restricted war zone, which is the basis for Australia’s Foreign Fighter Act’.

Thus, it seems that the consequences for an individual fighting in a foreign conflict are more likely to be driven by the political allegiances of their country of citizenship or residence than by international law. This approach seems to violate cardinal legal principles: certainty and equality in application. Is there a way to provide greater legal clarity at the international and national level and resolve the current tension between national and international law? Dill points to the need for the law to adapt but underlines the difficulty of changing international treaties: ‘We do need to continuously update legal models and laws, whether due to the changing nature of war, the increased presence of non-state actors with large militias, and the emergence of new technology; however, in the world of treaties, this is not an easy task.’

Updating laws is indeed not easy when the proliferation of foreign fighters in recent decades has gone hand-in-glove with technological advances that make communication, and therefore recruitment, faster, simpler and less open to scrutiny. It is also easier for fighters to move from conflict to conflict, from Afghanistan to Syria or Iraq, or to Israel, Russia and Ukraine. Meanwhile, the difficulty of monitoring the activities of an individual in a far-flung land or collecting evidence for prosecution back home should they be suspected of war crimes, remains. Steven Kay is a Member of the IBA War Crimes Committee Advisory Board. ‘Barriers to prosecution might be whether the prosecution can obtain admissible evidence to UK court standard; if the national authorities of the foreign state prevented UK authorities or even the defence from investigating or obtaining witnesses so that a fair trial could not be held’, Kay says.

And, as Rosenblatt points out, identifying returned US citizens potentially responsible for war crimes overseas is a challenge: ‘Those fleeing accountability, especially those with financial means, might successfully be able to hide out in the United States. The example from other countries shows that perpetrators are often identified when they are physically proximate to victims of their atrocities. For example, some Syrian war crimes suspects were identified and arrested in Germany and Sweden after they were seen on the streets of those cities by Syrian crime victims who also ended up in Germany.’

Then there is the question of who is responsible for the prosecution of war crimes, as Kay points out in relation to allegations of war crimes committed in Gaza: ‘The primary jurisdiction would be Israel if they have committed war crimes or crimes of universal jurisdiction […] If Israel failed to prosecute and the UK had evidence of its citizen committing an offence it could prosecute and if it failed to do so the ICC might prosecute.’

What can be done about this ‘free-floating threat to international security’, as Professor Benjamin Farley of Emory University School of Law describes foreign fighters? Trying to distinguish between mercenaries, ‘foreign terrorist fighters’ and other foreign fighters seems to have led down a blind alley. Is the solution, perhaps, for states to ban their nationals from fighting in a foreign army, whatever the motivation, as does Switzerland?

But then how feasible is it to enforce a ban? For such a moratorium to be credible it would have to be clear that there would be no political ‘amnesties’ and that foreign fighters would indeed always be prosecuted. But such rigid action risks public unpopularity in certain circumstances – it is hard to imagine broad public support in Western countries for prosecuting fellow citizens who fought against brutal terrorists like ISIS.

Given the variety of motivations of fighters (such as ideology, religion, ethnicity or money) and the complex matrix of political and legal considerations in an increasingly interconnected world, an observer might be excused for concluding that there is no solution which would eradicate the presence of foreign fighters on the battlefield. Vested political interests in the outcome of a war, imprecise or limited legal definitions and acceptance of the concept of dual nationalities are just some of the factors which militate against a comprehensive and effective response to the phenomenon of citizens going abroad to fight.

And, as Dill notes in relation to Ukraine, the problem is only likely to grow. ‘I would predict that the more visible presence of mercenaries and foreign fighters in the war in Ukraine will significantly increase efforts to examine shortfalls or areas where the law may need to be reformed’, he says. But where credible evidence exists of systematic war crimes being committed by a party to a conflict (even pending final determination that this is the case), perhaps a useful first step would be for countries to forbid their citizens to join such a fighting force, making it clear that they will be prosecuted if they do.

Anne McMillan is a freelance journalist and can be contacted at basestation2011@gmail.com