Thousands of relatives of those murdered in the worst European atrocity since the Second World War gathered yesterday to remember them, in Srebrenica. The death toll from the massacres in what was meant to be a UN-protected safe haven for Bosnian Muslims in July, 1995, is 8,372. But bodies are still being unearthed. Names are still being added to the list of the dead.

The men who ordered the killings, Ratko Mladic and Radovan Karadzic, remain at large. For 13 years they have been protected not by vast deserts or impenetrable mountains, but by people who refuse to accept the overwhelming evidence that they are war criminals.

Guilt for war crimes does not expire. The most recent suspect is Omar al-Bashir, the Sudanese President, who is expected to be charged next week by the International Criminal Court with crimes against humanity and genocide for atrocities committed in Darfur. At the other end of the spectrum, Aribert Heim's responsibility for his butchery of fellow humans at the Mauthausen concentration camp is not diminished by his age, now 94. Messrs Ratko and Mladic have reason to believe they can defy civilisation in the same way, without even fleeing to the Andes. The UN-administered International Criminal Tribunal for the Former Yugoslavia (ICTY) is supposed to complete its trials by the end of this year and its appeals by 2010. Its chief prosecutor has given warning that these deadlines will be missed. In principle, this could mean more time to hunt Europe's most-wanted men. In practice, the most likely outcome is bickering at the UN. Worse, Russia is calling for the tribunal to be wound up. Like Serbia's nationalists, it considers the ICTY biased. This week Moscow claimed that the recently overturned conviction of Naser Oric, a Bosnian Muslim commander jailed for failing to prevent the killing of Serbs, proved the point.

It did nothing of the sort. There is no dispute that atrocities were committed by all sides in the Bosnian war. This imposed a fundamental duty on the ICTY to strive constantly and consciously for real justice, not victor's justice. It was not perfect, but it did strive - above all to collect hard, scientific evidence. In the case of Mr Oric and another senior Bosnian Muslim it has concluded on appeal that there was simply not enough evidence to convict. For those accused in relation to Srebrenica, the evidence is unarguable. It consists not just of thousands of witness statements, but military documents, exhaustive ballistics analysis, satellite imagery of mass graves and the teeth and DNA of thousands of exhumed bodies.

A new Government was sworn in this week in Belgrade, which refuses to recognise Kosovo's independence but professes to be pro-European. In particular, its justice minister and chief prosecutor have made new promises that Messrs Ratko and Mladic will be handed over. It is time for Belgrade to make good on those promises; for the UN to assist by extending the ICTY's lifespan; and for signatories to the International Court of Justice to consider amending its charter so that, if necessary, it could hear war crimes cases dating from before its establishment in 2002.

The men responsible for Srebrenica can run, but they cannot hide forever. Their surrender would unblock Serbia's vital EU accession talks. More importantly, it would bring, at last, some moral restitution for their victims.