Legal challenge: Migrant rules best tool as law remains ineffective

A concerted campaign, led by the Aegis Trust, to strengthen war crimes legislation succeeded in changing the law shortly before the Labour government left office.

Prior to the law change, suspects could only be prosecuted if they committed an alleged war crime after 2001 – a cut-off point which ruled out several earlier atrocities, including the 1994 genocide in Rwanda. The law now backdates offences to 1991.

A second loophole which allowed suspects defined as non-UK residents – such as those in the country on visas – to avoid potential prosecution has also been tightened.

The law changes came into force on April 6 and it is too early to judge what their effect might be. However, since 2001, when Labour first broadened the compass of war crimes legislation, it has been easy to keep count of the number of prosecutions in the UK: Zero.

The only successful prosecution of anyone committing what could be described as a crime against humanity was that of Afghan warlord Faryadi Zardad in 2005.

He was found guilty of torture and hostage taking at the Old Bailey and sentenced to 20 years in prison, though technically he was charged under separate laws specifically relating to torture and hostage taking.

Prosecuting any suspected war criminal presents far greater challenges in relation to evidence than most other offences.

For human rights campaigners, victims and many others, prosecution remains the preferred option. But given the difficulties, the onus is on the Home Office to get its immigration screening right.

Campaigners also believe the government could look closely at using immigration law as a means of bringing a degree of accountability to suspected war criminals who can't be prosecuted for their primary offences.

Nick Donovan,of the Aegis Trust, believes the legal requirement for anyone going through the immigration system to tell the truth could provide scope to prosecute if a suspected war criminal was found to have lied to either gain refugee status or in an attempt to gain citizenship.

This approach is pursued vigorously in the US and "would at least give victims a chance to see the perpetrators in court", he said.