The arrest of Radovan Karadzic, the wartime Bosnian Serb leader, is good news for peace and stability in all the former Yugoslav republics as well as the entire Balkan region, but it is particularly welcome news for the European Union which has made the capture of alleged war criminals a pre-condition for Serbia to be considered for EU membership.

Karadzic's capture is also good news for justice and the rule of law, and will send a strong message to international leaders who are suspected of genocide and crimes against humanity - international law will eventually catch up with them.

That Karadzic was captured after 13 years on the run is quite extraordinary in itself, yet what is even more bizarre is that he was not found hiding in some remote area of the Bosnian Serb Republic but living a normal life - under heavy disguise - in Belgrade. Sporting a huge white beard and heavy glasses the former psychiatrist had changed his name to Dragon Dabic and had been practicing as an alternative medicine doctor.

There can be no doubt that Karadzic had enjoyed the protection of friends in high places in Serbia (where some people still consider him a hero) over the years. Yet the political atmosphere in Serbia has been slowly changing to one which favours more co-operation with the EU and Karadzic's arrest came soon after a pro-EU government coalition formed in Belgrade and after pro-EU president Boris Tadic had appointed his own man as head of the country's intelligence service.

So far there have been 56 convictions at the United Nations Hague Tribunal in connection with war crimes committed during the war in former Yugoslavia. However, those who have been convicted include generals, warlords and militia leaders, but none of the masterminds behind the conflict. Former Yugoslav president Slobodan Milosevic died while being tried at The Hague and therefore escaped conviction. The arrest of Karadzic offers the international community the chance to convict a person charged with orchestrating the atrocities of the Bosnian war.

Karadzic's notoriety is mainly due to his alleged role in the murder of 8,000 Bosnian men and boys in Srebrenica in 1995 - Europe's worst post-war atrocity - and in the siege of Sarajevo in the Bosnian war. He is officially charged with 11 counts of genocide, war crimes, crimes against humanity and other atrocities; the shelling of Sarajevo during the city's siege, in which 12,000 civilians died; organising the massacre in Srebrenica; targeting Muslim and Croat political leaders, intellectuals and professionals in Bosnia; ethnic cleansing, and destroying homes, businesses and sacred sites.

The EU deserves credit for the constant pressure it exerted on the Serbian authorities to bring Karadzic to justice by dangling the prospect of EU membership as a reward. The fact that the authorities in Belgrade finally co-operated shows just how relevant the EU is as a force for good on the international stage and how important the prospect of EU membership is for non-EU members.

It also proves that a 'carrot and stick approach' often does produce positive results in international politics. Some observers have pointed out the lack of such an approach in Sudan where the international community has taken no action. Nor has it promised any rewards to convince the country to hand over its President, Omar al-Bashir, to the International Criminal Court to face charges over genocide in Darfur.

Needless to say, the EU warmly welcomed Belgrade's arrest of the former Bosnian Serb leader. French foreign minister Bernard Kouchner remarked: "Everyone is jumping for joy - finally, finally. It's certainly a good thing for bringing Serbia closer to the European Union." German chancellor Angela Merkel said: "A historic moment. The victims must know: massive human rights violations will not go unpunished."

However, nobody is expecting Serbia to join the EU overnight, for a number of reasons. First of all another alleged war criminal, former Bosnian Serb army commander Ratko Mladic, who is also linked to the atrocity at Srebrenica, is still at large and is wanted by the UN court.

Also, France and Germany have made it clear that there can be no further EU enlargement until the Lisbon Treaty is approved. Furthermore, Serbia is still a long way off in terms of bringing its economic and political structures in line with the EU. And of course there is the problem of Kosovo. One wonders whether the EU will be willing to admit a second member, after Cyprus, with an unresolved territorial dispute.

On the other hand it is clear that a new chapter has begun between the EU and Serbia. In April the two sides signed a pre-accession agreement which was on hold until Serbia was believed to be cooperating in tracking down alleged war criminals. Serbia can now expect to be declared an EU candidate country by the end of this year and this is excellent news for the stability of the entire Balkan region. The arrest of Karadzic shows just how relevant the EU is in the Balkans, and perhaps more importantly, how the offer of EU membership leads countries to embrace European values of justice and human rights.