Human rights exceptionalism. The war in Iraq has hurt Americans in many ways: increased our taxes, decreased our civil liberties, killed our relatives and peers, reduced our public services, resulted in racial hysteria, damaged our economy, thrown our government into insurmountable debt, and made us less secure at home and abroad.
European governments are also catching some harm for their role in assisting the U.S.' less savory activities associated with the so-called war against global badness. Europe under 'rendition' cloud (news.bbc.co.uk, 6/7/06) notes that not only have Poland and Romania tarnished their international reputations by hosting U.S. 'black' facilities, where untold human rights violations have occurred, but Sweden, Bosnia, the UK, Italy, Macedonia, Germany and Turkey have all aided and abetted the U.S. in a variety of ways. This puts the EU in an awkward position of wanting to enforce human rights everywhere, but having its own members shun that responsibility at key points in its dealings with the U.S. government.
The goal of the investigation is to prevent these sorts of human rights violations from occurring again. But with the violator countries unwilling to admit their guilt, it's hard to get to a point where such events can be prevented with any certainty.
Who wants to be a citizen of a country whose government 'disappears' its citizens, or who permits other governments to 'disappear' citizens to undisclosed locations in its country?