Taylor was convicted for "aiding and abetting" in war crimes and crimes against humanity, but this threshold is not a high one. This same standard could potentially be applied to other heads of state that might be culpable for aiding and abetting crimes within their territories or elsewhere.

That might include, for example, Ugandan President, Yoweri Museveni, who is alleged to support the Union of Congolese Patriots (UPC), which committed crimes in eastern Congo's Ituri province, or Rwandan President Paul Kagame for his support of the National Congress for the Defence of the People and its crimes in Congo's Kivu region.

These two central African rulers supported crimes that fall within the jurisdiction of the International Criminal Court. In fact, the court secured its first-ever conviction just in March; against UPC founder Thomas Lubanga for use of child soldiers. Museveni and Kagame both heavily supported the UPC.

Yet the ICC (which is separate from the Special Court for Sierra Leone) has not indicted Museveni or Kagame. There are a few reasons, which reveal how the ICC functions and how it doesn't.

To investigate crimes within any country, the ICC needs one of three things: (1) to be invited in by a state that has signed up to it, (2) to assert jurisdiction of its own volition in a country that has signed up to it, (3) or to have its jurisdiction imposed on a state by the United Nations Security Council. Savvy leaders such as Museveni have been able to play to the ICC's dependence on state cooperation -- any exhaustive investigation would require the cooperation of the host government. So, after negotiating referral from Museveni to investigate abuses in Uganda, the ICC investigated Joseph Kony's Lord's Resistance Army, a stated U.S. target. But it has not pursued war crimes and crimes against humanity committed by the Ugandan Army, a U.S. ally. In 2002, a U.S. official threatened the court with obstruction if it pursued cases such as that against Museveni.

Thorough investigations require access to witnesses, documentation, crime scenes, and of course the physical apprehension of the accused. An unfriendly host government can deny all of these things.

According to Sierra Leone's Truth and Reconciliation Commission, the Revolutionary United Front (a Taylor-sponsored rebel group) committed 57 percent of the crimes in Sierra Leone's war, the Sierra Leonean army (whose allegiance has changed between the RUF and the government) committed 30 percent, and government-aligned Civil Defence forces 12 percent. Only 1 per cent of crimes were committed by West African peacekeepers, although they were only present in Sierra Leone for small parts of the conflict.

The UN-backed Special Court was empowered to prosecute "those bearing the greatest responsibility" for the war's crimes. But the Special Court was barred (see Article 1) from prosecuting British personnel that supported crimes by the Civil Defence Forces. The prosecution did not seriously investigate Sierra Leone's President, probably for fear that it would lead him to stop cooperating with other parts of their investigation. The Sierra Leonean president also seconded Sierra Leonean police officers to undertake the Special Court's investigations into crimes by the Civil Defence Forces.