Introduction

This chapter focuses on an issue which was the subject of some of the earliest international laws affecting the welfare of human beings and which remains a key subject of international human rights law today: slavery. Slavery has persisted throughout most of human history and the US Supreme Court recognised in 1825 that the slave trade was: “sanctioned in modern times by the laws of all nations who possess distant colonies”.

Anti-Slavery International is recognised as the world’s oldest international human rights organisation, and international efforts to combat slavery and the slave trade date back to the late eighteenth and early nineteenth centuries. European States came together at the end of the Napoleonic Wars for the Congress of Vienna in 1815, where they declared an intent to “consider the universal abolition” of the slave trade (as explained by Jean Allain). In subsequent decades Britain agreed bilateral treaties to tackle the slave trade at sea. Jenny Martinez has argued that the resulting “slave trade courts [known as ‘Mixed Commissions’] were the first international human rights courts”, and that they freed almost 80,000 enslaved people held on illegal vessels. However, it was not until the 1885 General Act of the Berlin Conference and the 1890 General Act of the Brussels Conference that multilateral international agreements to tackle the slave trade were reached. Even then, the condition of slavery itself was not outlawed (the focus was instead on the slave trade and accordingly on preparatory acts leading to enslavement). The Treaty of Peace signed at Saint-Germain-en-Laye in 1919 contained a commitment to: “endeavour to secure the complete suppression of slavery in all its forms and of the black slave trade by land and sea”, but endeavouring to suppress slavery was still some way from actually prohibiting slavery. Eric Williams contended that the private interests of capital-holders, rather than humanitarian interests, lay behind the gradual move to outlaw slavery. Nevertheless, significant progress was made combatting slavery following the second world war. Enslavement is now an internationally acknowledged crime against humanity (Art 7(1)(c), Rome Statute), and the prohibition of slavery is an obligation erga omnes and a jus cogens norm.

Despite being firmly outlawed, however, slavery remains a significant global problem. Slavery and similar practices (including servitude, forced or compulsory labour and human trafficking), which are often described under the umbrella term ‘modern slavery’, continue to cause substantial harm. The Walk Free Foundation has estimated that around 50 million people are trapped in modern slavery. This is an ongoing concern of international human rights law because, although States do not usually deliberately and directly enslave people any longer, States are still obligated to protect people against slavery-like practices by non-State actors and to prevent future harm (and in fact States are still sometimes complicit in slavery, as can be seen in the Koraou v Niger case). This chapter discusses the historical development of the prohibition of slavery in international human rights law and the resulting obligations now faced by States. Section 1 begins with the League of Nations’ Slavery Convention of 1926, which provided the first internationally recognised definition of slavery, and it discusses the International Labour Organization’s 1930 Forced Labour Convention and the Supplementary Slavery Convention of 1956. Section 2 then describes the international and regional prohibitions of slavery, servitude and forced and compulsory labour post-second world war. It also considers the meaning of servitude. Finally, section 3 considers the prevalent place of human trafficking within the present discourse on modern slavery and the legal obligations faced by States in light of this, as well as the rights and protections given to individuals to guard against modern slavery and prevent future harm.

Slavery and Forced Labour

This opening section considers the definitions of slavery and forced or compulsory labour which were established under international human rights law during the interwar period, before then explaining in section 2 how these important concepts came to be universally prohibited.

Slavery

In 1926 the League of Nations’ Slavery Convention saw the international community agree a definition of slavery for the first time (Article 1(1)):

This definition remains the starting point for international jurists when addressing slavery. The Slavery Act was limited, though, because it required only that slavery be abolished (Article 2(b)):

The slave trade, which was to be prevented and suppressed without any clause requiring that this be done ‘progressively’ (Article 2(a)), was defined separately from slavery as (Article 1(2)) including:

The 1956 Supplementary Slavery Convention reproduced (at Article 7(a)) the original definition of slavery and provided examples of further slavery-like practices. The 1956 Convention also maintained the ‘progressively and as soon as possible’ qualification (Article 1), but it did mandate that the slave trade and enslavement be subject to criminal sanction under the domestic laws of contracting States (Article 3).

A significant question about the 1926 Article 1(1) definition arose, in light of slavery being outlawed, because it was important to determine whether a person may be subjected to slavery even in the absence of a formal title conferring legal ‘ownership’, as had generally been the case with historic chattel slavery. In its first case considering the meaning of slavery, Siliadin v France, the European Court of Human Rights (ECtHR) deemed [at 122] that evidence of formal legal ownership was necessary for slavery to have taken place. However, this fails to recognise that slavery may result from powers attaching to the right of ownership and that such powers may be the result of either a person’s formal legal de jure ‘status’ or their non-legal de facto ‘condition’. The United Nations set out the following six factors which may be indicative of ‘powers attaching to the right of ownership’, and which may indicate that a person’s condition amounts to slavery:

The International Criminal Tribunal for the Former Yugoslavia (ICTY) considered whether the crime of enslavement had been committed in its Kunarac judgment, despite the lack of any legal title. The ICTY found [781] that formal de jure ownership was not necessary and that evidence of de facto ownership, i.e. evidence of a person exercising control tantamount to ownership even without legal title, could be sufficient to constitute enslavement. There was no requirement for an acquisition or purchase to have taken place. A similar approach was adopted by the High Court of Australia in the Tang case, which focused on establishing whether effective ownership had been exercised rather than on whether there was formal legal ownership [148]. The Inter-American Court was also clear in its Hacienda Brasil Verde Workers v Brazil judgment that: “the existence of a formal document or law is not essential to characterize the phenomenon [of slavery], as in the case of traditional or chattel slavery” [270]. That Court considered that (i) ‘status or condition’ refers to either de jure ownership or de facto ownership, and both may amount to slavery; and that (ii) ‘powers attaching to the right of ownership’: “should now be understood as constituting control over a person in such a way as to significantly deprive that person of his or her individual liberty” [271]. As Jean Allain explained, slavery can also involve the destruction of a person’s juridical personality, so that an enslaved person has no standing before the law and is effectively reduced to an object. Allain helped develop the Bellagio Harvard Guidelines, which give further examples of de facto forms of slavery. The foregoing interpretations show that the international legal definition of slavery remains very relevant today. Slavery can still happen even though the practice is universally outlawed so that no lawful purchase of an enslaved person can occur any longer.

Forced Labour

Forced or compulsory labour was defined separately at Article 2(1) of the International Labour Organisation’s 1930 Forced Labour Convention:

This may appear more easy to establish than the slavery definition. Seemingly any form of work, done under (i) ‘the menace of any penalty’ which was (ii) not done ‘voluntarily’, may amount to forced or compulsory labour. The penalty may be in the form of physical violence or restraint but may also be psychological, and prior consent to work does not necessarily negate involuntariness (as explained in Chowdury v Greece [96]). The definition becomes more complicated, though, because Article 2(2) set outs situations which will not amount to forced or compulsory labour despite otherwise satisfying the above definition:

Article 11(1) also qualifies that: “Only adult able-bodied males who are of an apparent age of not less than 18 and not more than 45 years may be called upon for forced or compulsory labour”; and that less than twenty-five percent of men should be in forced or compulsory labour for fewer than sixty days per year. Similarly to the Slavery Convention, the Forced Labour Convention did not aim to immediately abolish forced labour, but instead to (Article 1(1)): “suppress the use of forced or compulsory labour in all its forms within the shortest possible period”. The Forced Labour Convention may be understood as regulating rather than abolishing forced labour because it set out situations when forced labour may be deemed appropriate.

The 1930 definition of forced labour was reaffirmed in the 2014 Protocol to the Forced Labour Convention. The Protocol confirms that contracting States will (Article 1(1)): “take effective measures to prevent and eliminate its use, to provide to victims protection and access to appropriate and effective remedies, such as compensation, and to sanction the perpetrators of forced or compulsory labour”. The signatory States also agreed to educate potential victims and employers, and to not prosecute or impose penalties on victims of forced labour (Article 4(2)). The Protocol provides much firmer protection against forced or compulsory labour than the 1930 Convention did, though the original 1930 definition remains.

Both slavery and forced or compulsory labour were prohibited under international human rights law following the second world war, and the definitions set out in 1926 and 1930 remain in use today. The extent of those prohibitions is explained in the next section.

Prohibitions of Slavery, Servitude and Forced Labour

International and regional efforts to prohibit slavery moved forward at pace post-1945. Six separate international and regional agreements containing absolute prohibitions of slavery and slavery-like practices are set out below:

There are clear similarities amongst, and important differences between, the above six agreements. Each provides a firm commitment to prohibiting slavery and / or similar practices in absolute unqualified terms (although the UDHR and ASEAN Declaration are non-binding), while the details differ. The UDHR prohibits slavery and servitude but, like the ACHPR and the ASEAN Declaration, it does not mention forced or compulsory labour. The ACHR prohibits ‘traffic in women’ and the ASEAN Declaration prohibits ‘human smuggling or trafficking in persons’, but none of the other agreements mention human trafficking. The ECHR prohibits forced or compulsory labour, but then delimits the meaning of forced labour similarly to the Forced Labour Convention so that not all practices which seemingly meet the forced labour definition will in fact be prohibited. The prohibition against forced or compulsory labour is absolute but certain exceptions, including military service, lawful detention and emergency situations, will mean that the forced or compulsory labour definition is not satisfied. This approach is repeated in the ICCPR and ACHR. The ACHPR is unique in prohibiting slavery and the slave trade under the same provision which prohibits torture, cruel, inhuman or degrading punishment and treatment. The ACHPR explicitly links freedom from slavery to respect for human dignity and, though it does not mention forced or compulsory labour or human trafficking, it does prohibit ‘all forms of exploitation’.

Servitude

All of the above agreements except the ACHPR mention servitude. The ICCPR contains a specific clause at Article 8(2) prohibiting servitude, whereas the other agreements link slavery and servitude together without containing a separate clause in respect of servitude. Unlike with slavery and forced or compulsory labour, there is no specific internationally agreed definition to turn to for servitude. The Supplementary Slavery Convention provides examples of practices similar to slavery, which may amount to servitude (Article 1):

The ECtHR has issued general guidance in respect of Article 4 of the ECHR which explains that servitude: “means an obligation to provide one’s services that is imposed by the use of coercion, and is to be linked with the concept of slavery”. The ECtHR explained in its Siliadin v France judgment that servitude involves a: “particularly serious form of denial of freedom” [123] which may involve a person being required to live at another person’s property and where their condition seems permanent. Unlike slavery, though, servitude does not necessitate some form of ownership. As well as being akin to slavery, servitude has also been regarded by the ECtHR as an aggravated form of forced or compulsory labour (C.N. and V. v France [91]). The distinction between slavery, servitude and forced or compulsory labour will not always be clearcut in a given case, but it is clear that when any of these practices take place they are prohibited in absolute terms by international human rights law. Although the ACHPR does not mention servitude specifically, it prohibits ‘all forms of exploitation’ and this must include any situation amounting to servitude or forced or compulsory labour. The former UN Special Rapporteur on contemporary forms of slavery, Gulnara Shahinian, reported (para 25) that slavery is not to be regarded automatically as a more serious form of exploitation than servitude. In this sense the prohibition of slavery, servitude and forced labour differs from the prohibition of torture, inhuman and degrading treatment because the former is not necessarily assumed to be hierarchical. Having considered the precise terms of the prohibitions of slavery, servitude and forced or compulsory labour under international human rights law, the next section looks at how this works most often in practice today with focus on the development of anti-human trafficking laws.

Human Trafficking

In the decades following the second world war up to the turn of the millennium the prohibition of slavery received scant attention in international human rights law. Of the fifty-five cases cited in its guidance on Article 4, the ECtHR only referenced twelve from prior to 2000. Of those twelve cases, the main focus was on forced or compulsory labour and some of the cases involved professionals (including dentists and lawyers) disgruntled at their working requirements. James Hathaway was critical of the Human Rights Committee, supervisory body to the ICCPR, because it had only referred to Article 8 in three decisions up to 2008. It had also failed to issue a General Comment clarifying the meanings of slavery, servitude and forced or compulsory labour. It was as if the prohibition of slavery had largely disappeared from the international human rights law landscape.

The Palermo Protocol

This changed after 2000, however, with the UN’s Protocol to Prevent, Suppress and Punish Trafficking in Persons Especially Women and Children, supplementing the United Nations Convention against Transnational Organized Crime (the “Palermo Protocol”). This began a renewed focus on preventing human trafficking and modern slavery as linked concerns. States agreed for the first time a definition of human trafficking:

The Article 3(a) definition of human trafficking is more akin to the 1926 definition of the slave trade than it is to the definition of slavery. It can be broken down into three parts: (1) ‘action’; (2) ‘means’; and (3) ‘purpose’.

1.  Human trafficking must begin with an action, which may be either the: ‘recruitment, transportation, transfer, harbouring or receipt of persons’. This is quite wide-ranging and need not necessarily involve movement across an international border. Trafficking can be ‘internal’, i.e. there is no requirement for a State’s borders to have been crossed.
2. The action must have been induced by some means, consisting either: ‘the threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person’. If such means have been employed then a person’s consent to exploitation ‘shall be irrelevant’ (Article 3(b)). Note also that any child, aged under eighteen, need not demonstrate the means element of the human trafficking definition owing to their heightened vulnerability to exploitation. A child should be acknowledged as a victim where a qualifying action took place for the purpose of relevant exploitation (Articles 3(c) and (d))
3. The action and means must have been deployed ‘for the purpose of exploitation’. Examples of relevant exploitation are: ‘the prostitution of others or other forms of sexual exploitation, forced labour or services, slavery or practices similar to slavery, servitude or the removal of organs’. The UN Office on Drugs and Crime has issued guidance confirming that the examples provided at Article 3(a) should not be regarded as an exhaustive list, and this is confirmed by the use of the term ‘at a minimum’. The guidance explains that the list of examples may be expanded, but that: “there are some limits, which may potentially include a threshold of seriousness that operates to prevent the expansion of the concept of trafficking to less serious forms of exploitation such as labour law infractions. It should be noted, however, that the Protocol does not clearly establish any such threshold” (page 8). Hence, there is a minimum level of severity to be expected before exploitation would be serious enough to constitute human trafficking, but that minimum level of severity is not clearly set out within the Palermo Protocol. The exploitation need not have come to fruition so long as the action was done for the purpose of exploitation.

The Palermo Protocol focused primarily on tackling the crime of human trafficking, including the needs: to criminalise those responsible for human trafficking (Article 5); to police borders (Article 11); to secure travel documents (Articles 12 and 13); and for States to co-operate to combat human trafficking (Article 10). It also contains some limited protections and entitlements for victims, such as: ensuring anonymity (Article 6(1)); adopting measures to assist their “physical, psychological and social recovery” (Article 6(3)); and requiring contracting States to consider allowing non-citizen victims of human trafficking to remain within their territories.

Anne Gallagher explained that the UN adopted the Palermo Protocol alongside the Smuggling Protocol as: “part of a package of legal instruments which were developed by the UN’s Crime Commission to deal with the growing problem of transnational organised crime”, which has: “made it difficult to persuade governments to place individuals and their rights at the centre of this debate”. Unlike human trafficking, the human smuggling definition focuses specifically on the movement of people across borders: “”Smuggling of migrants” shall mean the procurement, in order to obtain, directly or indirectly, a financial or other material benefit, of the illegal entry of a person into a State Party of which the person is not a national or a permanent resident” (Article 3(a) of the Smuggling Protocol). Although human trafficking and smuggling are sometimes conflated, the definitions are very different. Smuggling need not involve exploitation and, unlike human trafficking, smuggling need not necessarily involve the abuse of fundamental human rights.

Historic Anti-Trafficking Laws

Anti-human trafficking laws developed separately from laws aimed at tackling slavery. Human trafficking had been a concern of international law from as long ago as 1904, when European States adopted the International Agreement for the Suppression of the White Slave Traffic. For Federico Lenzerini this was early evidence of a victim-centred approach because States sought to protect women from being transported across borders for the purpose of prostitution, but it may also be understood as a precursor to increasingly stringent migration control and strict policing of state boundaries. The 1910 International Convention for the Suppression of the White Slave Traffic provided for the criminal punishment of people procuring or enticing women and girls into prostitution; and the International Convention for the Suppression of the Traffic in Women and Children, adopted by the League of Nations in 1921, abandoned the label ‘white slavery’ and extended protection against forced prostitution to male children as well as women and girls. In 1933, the International Convention for the Suppression of the Traffic in Women of Full Age extended the prohibition of trafficking for the purpose of prostitution to all women, regardless of whether they consented, and it helped facilitate the prosecution of traffickers in circumstances where their actions crossed State borders. This was extended further by the UN in 1949, as the Convention for the Suppression of the Traffic in Persons and of the Exploitation of the Prostitution of Others prohibited the trafficking of all persons, although protection remained restricted only to those trafficked for the purpose of prostitution.

Hathaway argued (page 44) that the Palermo Protocol was a product of this international legal history of combatting prostitution and cross-border movement, and he noted that some of the main advocates of modern anti-trafficking laws were conservative Christian groups, including President George W Bush, and anti-prostitution campaigners in the US. Hathaway was concerned that focusing on human trafficking would mean increased policing of state borders, while slavery itself would continue to be ignored and refugees would face harsher penalties for crossing those borders without permission. The key development with the adoption of the Palermo Protocol definition of human trafficking in 2000 was, as we have seen above, that it potentially encompasses a wide variety of forms of exploitation and is not focused only on prostitution. It places human trafficking within the human rights sphere by aiming to (Article 2(b)): “protect and assist the victims of such trafficking, with full respect for their human rights”. Although Marika McAdam cautioned that the human trafficking definition ought not to be applied outside its original context of combatting transnational organised crime, and that widening the definition beyond instances of serious crime risked undermining the international consensus and moral force behind anti-trafficking efforts.

European Convention Against Trafficking in Human Beings

The anti-trafficking cause was taken further after Palermo by the Council of Europe with the 2005 Convention on Action Against Trafficking in Human Beings (“ECAT”). ECAT repeats the Palermo Protocol definition of human trafficking and adds significant rights and protections for victims. The protections within ECAT are binding on signatory States but with some scope as to how each provision can be implemented domestically. Article 2 confirms, contrary to McAdam’s position, that ECAT: “shall apply to all forms of trafficking in human beings, whether national or transnational, whether or not connected with organised crime”. Article 10 emphasises the need to identify victims and for States to ensure that potential victims are not removed from their territories while full investigation and identification processes are underway. Article 12 requires States to provide assistance to victims (like Article 6(3) of Palermo) to aid their recovery, including access to emergency medical treatment and providing: “standards of living capable of ensuring their subsistence, through such measures as: appropriate and secure accommodation, psychological and material assistance”. Article 13 provides for a “recovery and reflection period” during which no action will be taken with a view to removing the victim from a State’s territory. Article 14 sets out circumstances in which it will be appropriate for States to issue residence permits to victims so that they may lawfully reside within their territories, either because (a) “their stay is necessary owing to their personal situation”; or (b) “their stay is necessary for the purpose of their co-operation with the competent authorities in investigation or criminal proceedings”. Article 15(3) requires that States ensure their domestic laws allow victims of human trafficking to claim compensation from perpetrators. Article 26 is also significant as it aims towards the “non-punishment” of victims of human trafficking, as contracting States must: “provide for the possibility of not imposing penalties on victims for their involvement in unlawful activities, to the extent that they have been compelled to do so”. Article 36 requires that contracting States’ implementation of ECAT be monitored by a group of experts on action against trafficking in human beings.

The 2010 ECtHR case Rantsev v Cyprus and Russia marked an important further development of the prohibition of slavery in international human rights law because the ECtHR decided that human trafficking fell within the ambit of Article 4 ECHR (the prohibition of slavery and forced or compulsory labour), even though human trafficking is not mentioned within the text of Article 4. The judgment explains [282]:

Vladislava Stoyanova criticised this approach and argued that the ECtHR should have expanded upon the international legal definition of slavery rather than deeming such analysis ‘unnecessary’. Her argument draws on concerns, as set out by Hathaway, that anti-trafficking laws are not specifically human rights-based and are more focused on tackling transnational crime and policing borders. However, the ECtHR’s approach in Rantsev has undoubtedly broadened the scope of protections now available to victims of modern slavery under Article 4 because anyone who is a victim of slavery, servitude, forced labour and / or human trafficking may be entitled to protection.

Rantsev concerned a female citizen of Russia, Oxana Rantseva, who had fallen from a balcony in Cyprus and died. She had entered Cyprus using an artiste visa, which meant that she had to perform as a dancer in a cabaret club. It empowered the owner of the club, MA, because Ms Rantseva’s right to reside in Cyprus was tied to her working for MA. Ms Rantseva left MA’s club, but MA located her. MA took Ms Rantseva to the Cypriot police where he reported her as an ‘illegal’ immigrant, handing them her passport, and wishing for her to be detained and returned to Russia. The police instead released Ms Rantseva; they required MA to take her back from the police station and returned her passport to him. MA then took Ms Rantseva to an apartment from where she fell and died with a handbag over her shoulder. Ms Rantseva’s father took the case to the ECtHR after an inquest in Cyprus deemed his daughter’s death an accident, and after failed attempts to have the Cypriot and Russian authorities cooperate effectively in investigating what had happened.The ECtHR noted [84] that Cyprus’s artiste visa regime was known to have facilitated the trafficking of women from former Soviet States for the purpose of sexual exploitation. Given the circumstances of Ms Rantseva’s case there were grounds for suspicion that she was a victim of human trafficking. As cited above, the ECtHR [282] did not deem it necessary to consider whether Ms Rantseva was a victim of slavery, servitude or forced labour, because she was a potential victim of human trafficking. The living instrument doctrine was applied, with reference to recent international legal developments marked by the Palermo Protocol and ECAT, to the effect that Article 4 ECHR could now be read as prohibiting human trafficking.

The ECtHR then set out the positive obligations faced by states which now attach to Article 4 in respect of the actions of non-state actors. States must protect people against slavery, servitude, forced labour and human trafficking by: (i) having an effective legislative and administrative framework [284]; (ii) taking certain operational measures where necessary [286]; and (iii) investigating effectively [288]. In respect of (i) the ‘legislative and administrative framework’ obligation:

This is significant as it extended states’ responsibilities beyond criminal law measures (as had been considered in the earlier Siliadin judgment) to business and immigration law. For (ii) the obligation to take ‘operational measures’:

This extends the operational measures obligation seen in Osman in respect of the right to life (see Right to Life Chapter) so that, for Article 4, the obligation will be triggered where there is a ‘credible suspicion’ of slavery, servitude, forced labour or human trafficking. Regarding (iii) the ‘procedural investigative’ obligation

The ECtHR also emphasised that an effective investigation will often require cross-border cooperation due to the transnational nature of human trafficking [289]. The focus here is on Article 4 ECHR but Rantsev also involved a breach of the right to life because Cyprus failed to conduct an effective investigation into Ms Rantseva’s death [242]. Cyprus breached the legislative and administrative framework obligation under Article 4 because its artiste visa regime was deemed to have failed to protect Ms Rantseva [293]. The ECtHR could perhaps have gone further on this point because the visa scheme was known to have facilitated human trafficking, rather than simply failing to protect people. Cyprus also breached the operational measures obligation because its police knew, or should have known, that the circumstances under which Ms Rantseva was presented to them gave rise to a credible suspicion that she may have been a victim of human trafficking. She was in police custody and so it was incumbent on them to take measures to protect her but instead they placed her at further risk of harm [298]. The ECtHR made no separate assessment of the investigative duty in respect of Article 4, having already found Cyprus to have breached Article 2 in that regard. Finally, Russia was also deemed to have breached Article 4 by failing to comply with the investigative obligation [309]. Russia was obligated to investigate Ms Rantseva’s recruitment as she had travelled on to Cyprus from there. This again confirms the obligation for States to cooperate when investigating human trafficking.

The Inter-American Court took note of Rantsev in the Hacienda Brasil Verde Workers judgment [at 287], which concerned the conditions faced by workers on a cattle ranch in Brazil. It found that the term ‘slave trade and traffic in women’ at Article 6(1) of the ACHR must now be interpreted in light of the Palermo Protocol and Rantsev to include all forms of human trafficking and not only trafficking of women [288]. The court also confirmed that States face enhanced obligations in respect of Article 6 ACHR and must act with due diligence because of the seriousness of the harm faced by victims of slavery, servitude forced labour and human trafficking:

Further Positive Obligations

The European Union agreed an Anti-Trafficking Directive in 2011 (amended in 2024) which is in similar terms to ECAT, and the ASEAN nations also agreed a binding 2015 Convention Against Trafficking in Persons, Especially Women and Children (“ACTIP”). Like Article 26 of ECAT and Article 4(2) of the Protocol to the Forced Labour Convention, Article 8 of the Anti-Trafficking Directive and Article 14(7) of ACTIP contain protections against punishment for victims of human trafficking who are compelled to offend. The then-UN Special Rapporteur on trafficking in persons, especially women and children, Maria Grazia Giammarinaro, issued guidance in July 2020 emphasising that this ‘non-punishment principle’: “must be given high-level prominence since it relates to the unassailable legal right of the victim to be protected by law” [para 9].

The issue of non-punishment of trafficking victims was taken up by the ECtHR in 2021 in the case of VCL and AN v UK. The case involved two Vietnamese children who had been trafficked to the UK for the purpose of criminal exploitation: they were forced to produce cannabis. Instead of seeking to identify them as victims and protect them, the UK authorities prosecuted, convicted and imprisoned them. VCL and AN appealed their convictions to the Court of Appeal, but were unsuccessful and so took their complaints to the ECtHR, which considered the Article 26 ECAT non-punishment provision and its relevance to Article 4 ECHR. Following Chowdury [104], a State’s positive obligations under Article 4: “must be construed in the light of the Council of Europe’s Anti-Trafficking Convention [ECAT]”. In VCL and AN the ECtHR decided that, while there is no absolute bar on prosecuting trafficking victims, such prosecutions can engage Article 4 because [159]:

The “early identification” of victims is therefore of “paramount importance” for any prosecution to be compliant with Article 4, and this is particularly important where the victim is a child [160]. Any decision to prosecute a potential victim of trafficking, i.e. where there is a credible suspicion that they are a victim, should “in so far as possible” await a decision by a qualified person confirming whether or not they are in fact a victim [161]. Then: “Once a trafficking assessment has been made by a qualified person, any subsequent prosecutorial decision would have to take that assessment into account. While the prosecutor might not be bound by the findings made in the course of such a trafficking assessment, the prosecutor would need to have clear reasons which are consistent with the definition of trafficking contained in the Palermo Protocol and the Anti-Trafficking Convention for disagreeing with it” [162]. The requirement to consider the trafficking assessment and provide reasons if departing from it was framed by the ECtHR as a positive operational measure obligation.

The UK was deemed to have breached the operational measure obligation because it prosecuted, convicted, imprisoned and then maintained the convictions of these two children without giving any clear reasons for doing so [183]. This was contrary to the expert assessment of the UK’s trafficking authorities, who had deemed that the children were victims of trafficking who had offended as a direct consequence of their trafficking experiences.

The ECtHR also examined ECAT in the Krachunova v Bulgaria. This time ECAT Article 15(3) was at issue: “the right of victims to compensation from the perpetrators”; and, again, the ECtHR deemed this to be a positive obligation under Article 4 ECHR. It was considered that denying victims the right to seek compensation would be analogous to the harm of prosecuting victims, as both may undermine victims’ recoveries and so both engage Article 4 [170-171]. The ECtHR also found that denying compensation might increase the risk of re-trafficking and that this was a further reason for obligating States to provide for the possibility of obtaining compensation [172].

Slavery, or the umbrella term modern slavery, remains a key concern of international human rights law today because of the changes brought about by the UN’s Palermo Protocol and the various regional agreements that have built upon it. The definition of human trafficking focuses on ‘exploitation’, a concept which is not clearly defined within the Palermo Protocol itself, and this means that many forms of harm which extend beyond the original concept of chattel slavery, and formal de jure ownership, may now be subject to absolute prohibitions under international human rights law.

Conclusion

The prohibition of slavery was fundamental to the development of, and remains a crucial principle of, international human rights law. The prohibition has changed substantially since 2000 as international human rights law now often focuses on human trafficking and the Palermo Protocol definition rather than on slavery itself. The 1926 Slavery Convention definition of slavery remains important, however, and is commonly understood as encompassing de facto as well as de jure forms of ownership, although the ECtHR has not been entirely consistent about this. Slavery, servitude, forced or compulsory labour and human trafficking are prohibited together under international human rights law as part of an overall prohibition of modern slavery. These developments have led to a widening of protections for victims. The prohibition of slavery under Article 4 ECHR encompasses protection against human trafficking even though human trafficking is not mentioned within the text of Article 4, and any victim of slavery would likely be able to show that they also meet the trafficking definition (particularly as slavery is included as one of the forms of exploitation prohibited by the Palermo definition). From after the second world war up to 2000 the issue of slavery had little impact in international human rights law, whereas after Palermo rights and protections have been developed and strengthened by way of regional judgments and binding agreements. The ECtHR’s and Inter-American Court’s recent judgments also show that States’ responsibilities to protect people extend far beyond the negative obligation not to put people into slavery. States’ positive obligations have recently been deemed by the ECtHR to have moved into the realm of protecting victims against criminal prosecutions and ensuring the right to compensation. Despite these recent developments, the 1926 Slavery Convention definition and the 1930 Forced Labour Convention definition remain fundamental to current understandings of the prohibition of modern slavery.

Further Reading

Jean Allain, Slavery Convention (Introductory Note), 2017

Anne Gallagher, ‘Human Rights and Human Trafficking: Quagmire or Firm Ground – A Response to James Hathaway‘, Virginian Journal of International Law (2009) Volume 49, Issue 4

James Hathaway, ‘The Human Rights Quagmire of Human Trafficking’, Virginian Journal of International Law (2008), Volume 49, Issue 1

Ryszard Piotrowicz, ‘States’ Obligations under Human Rights Law towards Victims of Trafficking in Human Beings: Positive Developments in Positive Obligations’ International Journal of Refugee Law (2012), Volume 24, Issue 2

SM v Croatia (App no. 60561/14) [2020]

European Court of Human Rights, Guide on Article 4 of the European Convention on Human Rights

Suggested Citation – Colin Gregory, ‘The Prohibition of Slavery’ in Stuart Wallace and Clare James (eds), Open Access International Human Rights Law (University of Leeds, 2026)