ONE of the first things we teach our students about public law is that the UK operates a “dualist system”. This means that public international law and municipal law are seen as separate entities, the rules of the first only operating internally when some legislative step has been taken to incorporate them into the second. Of how this works, criminal law would have traditionally provided the most obvious example. If, as often happens, the UK signs and ratifies a treaty under which the contracting States undertake to make a new form of conduct criminally punishable, a person committing it can only be prosecuted once legislation has been passed to add it to the ever-growing list of national criminal offences. (And likewise, until this happens, steps taken to prevent a person from committing such an act will not be justified as actions taken to prevent a crime: as the House of Lords held in the case of Jones and Others [2006] UKHL 16, [2007] 1 A.C. 136, when rejecting the argument of anti-war protesters who claimed their acts of criminal damage against air-force bases were justified as done to prevent “aggression”, behaviour which public international law treats as a crime.)

But what if the UK incurs an internationally binding obligation not to prosecute somebody for something? At first sight, one might have expected the same reasoning to apply, and that national criminal law would only cease to bite once legislation had been enacted to amend it. A growing body of case-law, however, suggests that different reasoning applies, and that a prosecution brought in breach of international obligations is liable to be halted. In Asfaw [2008] UKHL 31, [2008] A.C. 1061 the defendant had been convicted of an immigration offence committed in circumstances which the UN Refugee Convention required contracting States to recognise as a defence – an obligation which the UK had failed to implement by amending its immigration legislation appropriately. The House of Lords, by a majority, quashed the conviction on the ground that the prosecution should have been stayed as an abuse of process. The same approach has since taken by the Court of Appeal in a series of cases involving convicted persons claiming to be the victims of people-trafficking: the most striking of them L and Others [2013] EWCA Crim 991, [2013] 2 Cr. App. R. 23, which is the subject of this note.

In broad terms, people-trafficking is exploiting human beings commercially in ways that involve degrading treatment. Concrete examples include importing foreign women and forcing them to work in brothels, bringing in foreign juveniles to work as pick-pockets or as slave labourers in cannabis factories, and buying up surplus members of impoverished families to provide a source of organ transplants. To curb such practices, a range of international instruments have been adopted which, in a nutshell, require contracting States (of which the UK is one) to catch traffickers and hit them with a heavy hand, whilst treating their victims with understanding and compassion – inter alia, by not prosecuting them for criminal offences which they have been driven to commit. The first half of this equation the UK has enthusiastically embraced by creating a raft of new criminal offences. But the second half it has, to date, left to administrative arrangements and administrative discretion.

The four defendants in L and others had, it seems, dropped through the administrative net. Three were young men from Vietnam who had been prosecuted for cultivating cannabis, and pleaded guilty. After they had been sentenced, evidence emerged suggesting that they had been trafficked for the purpose. The fourth was a Ugandan woman who had been prosecuted for possessing a false passport. After her guilty plea and sentence, it then emerged that she had been trafficked for the purpose of forced prostitution. All four appealed, and the Court of Appeal, encouraged by the Crown, quashed all of their convictions.

In so doing, the Court relied on provisions of the 2005 Council of Europe Convention on people trafficking, and provisions of the 2011 EU Directive on the same topic (2011/36/EU, (OJ 2011 L 101 p.1), which in various forms of words require contracting States to protect victims of people-trafficking from prosecution or punishment for offences which they have been obliged to commit in consequence. Although these provisions, the Court said, confer neither immunity from prosecution nor in the case of prosecution a substantive defence,

Where, as in these four cases, this has not been done, criminal proceedings, said the Court, are liable to be stayed as an abuse of process. And if they are not stayed when they should be, the resulting conviction is liable to quashed.

Alas, as things stand today it seems that the victims of people trafficking fall through the administrative net quite easily. In March last year this was pointed out in a weighty report entitled It Happens Here, prepared by a Slavery Working Group commissioned by an independent think-tank, the Centre for Social Justice. Responding to this, as well as to a series of scandals well ventilated in the media, in December the Home Office published a Report (Cm 8770), to which a Draft Modern Slavery Bill is attached – a proposal which seems likely to result in legislation. Adopting suggestions in It Happens Here, the Draft Bill seeks to bring within one single legislative text all the existing offences relating to people-trafficking and slavery, which at present sprawl untidily across a range of different statutes, and it also proposes the creation of an Anti-Slavery Commissioner – in tabloid terms, a “Slavery Czar” – to co-ordinate the administrative effort. And predictably, it proposes to “send a signal” by raising the maximum penalties (already high) for offences of people-trafficking and slavery so that in future they will carry imprisonment for life.

No less predictably, however, the Draft Bill ignores the Centre for Social Justice's suggestion that there should be a legislative provision “for ensuring that victims of human trafficking are not prosecuted for crimes they may have committed as a direct consequence of their trafficking situation”. So in future this aspect of the matter will, as now, be regulated by the discretion to prosecute, reinforced by the power of the court to stay proceedings as an abuse of process.

This common law power to stay a prosecution as an abuse of process must surely be one of the most astonishing developments in the history of English criminal justice. Created fifty years ago, more or less accidentally, by a dictum from the House of Lords in Connelly v DPP [1964] A.C. 1254, it has grown into a virtually open-ended power in the courts to force a halt to any criminal proceedings which they feel to be fundamentally unfair. On the negative side, this creates uncertainty in the substantive law, and in criminal procedure, a new source of expense and delay. But on the positive side, it is – together with the discretion to prosecute and “jury equity” – an important instrument for ensuring that the over-sharp tooth of English criminal law is, where necessary, blunted.

That such devices lead to paradoxes goes without saying. One is the double-standard as to the impact of public international law which was mentioned at the beginning of this note. A bigger one is the resulting gulf between what the letter of English criminal law theoretically prescribes, and the way it operates in practice. When compared with the criminal codes of most of Continental Europe, English criminal law looks remarkably severe: both in the wide range of behaviour that it penalises, and in the narrow range of defences that it will accept. But in practice, happily, it usually contrives to be more or less humane.