You can run, but you can't hide from justice
The arrest of former Bosnian Serb military commander Ratko Mladic, for the murder of about 7,500 Muslim men and boys in Srebrenica in 1995, is a big step in the international effort to enforce the law against those who used to be free to murder and torture with impunity.
They were free to do so because the old rule was: kill your wife and you will be punished for murder. Kill thousands of innocent people while in the service of the state, and you will get a medal.
That ancient tradition was first challenged after the second world war, when leaders of the defeated powers were tried for war crimes and for the newly defined crimes of aggression and genocide. But it was an innovation with no follow-up - until the genocides in former Yugoslavia and Rwanda in the early 1990s forced the international community to act again.
In 1993, the UN Security Council set up the International Criminal Tribunal for the former Yugoslavia. The following year, a similar tribunal was created to investigate the genocide in Rwanda. But these were ad hoc courts to address specific crimes.
What was needed was a permanent international court to enforce the law against politicians and officials in countries where the government could not or would not try them in the local courts. The Rome Statute creating the International Criminal Court (ICC) was signed by over 150 countries in 1998, with effect in 2002.
The ICC has no jurisdiction over crimes committed before it was created, so Mladic will go before the tribunal for the former Yugoslavia, but it's really all part of the same institution. The main complaint against this new international legal system is that it moves too slowly - but that could actually be an advantage.
It took 16 years to track down and arrest Mladic, and his trial will probably take several more. That is a long time, but it also suggests an inexorability: eventually they will probably get you. That has a powerful deterrent effect.
Many suspect that the Sudanese regime's acceptance of the 'yes' vote in the recent independence referendum in the south was driven by fear among top officials in Khartoum that using force would expose them to the kind of ICC arrest warrant that has been issued for the president, Lieutenant General Omar al-Bashir, over the Darfur genocide.
Even after 16 years, the ICC got Mladic. It got most of the surviving organisers of the genocide in Rwanda. The likelihood of being pursued by the ICC represents a real risk for senior leaders who contemplate using force against their own people. They may do it anyway - consider Libya, Syria and Yemen at the moment - but it is nevertheless a genuine deterrent, and sometimes it saves lives.
Gwynne Dyer is a London-based independent journalist whose articles are published in 45 countries