The term “slavery” is not an arbitrary one. Over the years it has been codified in international law and to a somewhat lesser extent in national law. The key instruments in international law are the 1926 Slavery Convention, by the 1930 Forced Labour Convention, the 1956 Supplementary Convention on Slavery, the 2000 Palermo Protocol on trafficking, and the 2014 Forced Labour Protocol.

There are other important international laws related to this field, in particular on child labour and decent work, and there are important nuances within the slavery conventions I mentioned. But it is vital to note that this question of, “What is slavery?” is not a matter for social scientific contention of the sort so beloved by academics. It is something that has been established in international law as a result of considerable effort over the past 100 years to provide a robust framework for the continuing struggle against slavery. Remember how Lincoln had to struggle for a legal basis to end slavery in the United States. It is important to realise that we do not have to go back to that situation.

All this might seem like stating the obvious but I have been to more than one conference over the past couple of years with people who claim to be committed to eradication of contemporary slavery who have, for example, spent half an hour with the question “Is trafficking slavery?” and not once considered what the law on the question says let alone come to any convincing conclusion on the matter.

A good working definition of contemporary slavery comes from the 1930 Forced Labour Convention, which defines forced labour as all work or service extracted under menace of penalty, for little or no pay, for which the person in question has not offered themselves voluntarily. Trafficking is the technical process of moving people into situations of forced labour – so trafficking is indeed, by definition, slavery.

Part of the reason for the breadth of law in the international conventions is that contemporary slavery reflects a diversity of human experience: a life lived in bonded labour in Indian brick kilns is different in important respects from that of a Filipino domestic worker in London, or somebody in chattel slavery in West Africa, or a “restavek” child slave in Haiti, or a forced labourer in American agriculture. Hence the responses to these problems must be nuanced and adjusted to the realities of those particular abuses in the time which they occur

But in spite of the spectrum of experiences of contemporary and historical slavery empirical studies conducted by Anti-Slavery International and others indicate that slavery emerges at the conjunction of three common factors: individual vulnerability, usually, but not exclusively as a result of poverty; social exclusion; and failure of rule of law.

The issue of social exclusion and discrimination is a fundamental one in slavery: when we look at historical slavery in the Americas we see that racism was both a cause and a consequence of that slavery. In Latin America today many in forced labour are indigenous people. In Western Europe, including the UK, most people in slavery, but not all, are migrants. In South Asia most people in slavery are Dalits or from other scheduled castes or minority groups.

This is important for a variety of reasons, not least that it inhibits the issue from becoming a political one: if slavery is being inflicted upon groups and individuals who the wider society simply does not like, then that wider community is more likely to tolerate the abuses if they see them and not raise their voice to demand that governments do their jobs to stop the problem.

Consider the vitriolic abuse meted out to migrants by the UK’s press and politicians. This provides a glorious climate for those who wish to enslave vulnerable workers with impunity to do just that.

It is not the only contradiction at the heart of UK government policy on slavery. In spite of its public desire to become a world leader in the struggle against slavery the government’s policy confusion undermines this very ambition. In addition to its xenophobia against migrants they labour under the comforting delusion that increasing law enforcement powers while at the same time cutting law enforcement will be sufficient to counter the considerable powers that they have handed to unscrupulous employers to exploit and enslave workers. For example the Overseas Domestic Worker Visas, which determines the terms of work for around 15,000 people in the UK is a de facto license for trafficking for domestic servitude. Because if a migrant domestic worker leaves an employment relationship, irrespective of how abusive that relationship is, up to an including forced labour, then the rules imposed by the Home Office are clear. The worker will not be protected. They will be deported. That is an incredible power to put into the hands of unscrupulous employers.

And in spite of, or perhaps because of the evidence of institutionalised anti-migrant prejudice in the National Referral Mechanism, which is meant to identify victims of trafficking they refuse to include statutory protections for victims of trafficking in the modern slavery bill. Research by the Anti-Trafficking Monitoring Group found that if a person from the European Union presents themselves to the NRM a potential survivor of trafficking then there is a greater than 80% chance they will be recognised as such. If they come from outside the European Union then there is less than a 20% chance they will be recognised as such. That sort of imbalance in decision making can only be the result of institutionalised discrimination, something fed by the media and political elites who should instead be sanctioning those who disgrace their offices by privileging their petty bigotries over their responsibilities under the law.

Let us consider for a moment Tom Bingham’s eight principles of “Rule of Law”: that the law must be accessible and intelligible; that rights and liabilities should be resolved by law rather than discretion; that the law should apply equally; that minsters and public officers are bound by the law; that the law must provide protection of fundamental human rights, including, of course, an absolute prohibition on slavery; that access to the law should be affordable; that adjudicative procedures should be fair; and that states should comply with their obligations under international law.

In the UK today we have considerable evidence that the rights and liabilities are being resolved by the discretion, indeed the prejudice, of public officials; that the law is not being applied equally, with migrants from outside the EU in particular much more vulnerable to negative identification decisions; and a failure to, in effect, obtain that absolute prohibition on slavery. In other words UK policy on slavery, up to and including many of the measures included in the “modern slavery bill” are at odds with most fundamental principles of rule of law.

This is in part because the government insists on viewing the complexities of contemporary slavery from a prism of dangerous simplisticness that reduces the world to one of bad people to be thwarted by the good for the gratitude of the weak. Of course the world is more complex than that, filled with flawed people striving for decent work, where legal migration routes are sometimes the most dangerous, and where some businesses establish competitive advantage based on forced labour, and where some people enslave others because of their caste or ethnicity.

Given that it is important to recognise that the struggle against slavery must be must broader than a law enforcement approach. It must also consider advancing rule of law and combatting discrimination and prejudice. It must include victim protection, safe migration, ethical trade, and slavery-aware anti-poverty aid. Bluntly we need to reform unjust political, social and economic structures not just prosecute evil people.

The ideal of rule of law proposed by Tom Bingham is one that asserts the idea that the law, and indeed rule of law itself, should be about striving towards justice. I know this is not necessarily a universal view: I have seen the law used as a means of oppression, I’ve seen it used to uphold privilege and I’ve seen it asserted as a justification for itself alone. Looking across the world today we can see these same philosophies in practice and competition.

Indeed when we look at the debate around how the UK’s should grapple with the issue of contemporary slavery we can see these diverse philosophical views at odds again and in conflict around this single issue.

But a commitment to the ideals of human rights brings with it I believe that perspective of law as an instrument for advancing justice rather than those other diverse options, and this provides and important perspective from which to critically assess our progress towards this end.

As practicing lawyers you may encounter cases and clients where the law, or the practice of rule of law comes up short of justice. Your voice may not carry as much weight with government as that of business but the weight of evidence that you can introduce to the political discourse must, with time and effort help twist, in the words of Martin King, the moral arc of the universe towards justice.