The most famous Spanish investigative magistrate, Baltasar Garzon, launched an investigation into whether top Bush aides and lawyers should be charged (and prosecuted!) with war crimes over allegation of mistreatment of the Guantanamo detainees (click here to read the story: http://www.cnn.com/2009/WORLD/europe/03/29/gonzales.spain.gitmo/index.htm). Judge Garzon had already investigated Augusto Pinochet in the late 1990's, as well as other human rights abuses in former military regimes in Chile and Argentina; now he has turned his attention to the United States. In fact, judge Garzon just turned the criminal complaint against six U.S. officials - all of them high-level lawyers and executives within the Justice and Defense Departments under the Bush Administration - to prosecutors, who will decide within five days whether these individuals should be charged with war crimes and subjected to prosecution in Spain. The six officials include Alberto Gonzales, John C. Yoo, Douglas J. Feith, William J. Hayes II, Jay S. Bybee and David S. Addington.
This type of criminal prosecution is rare, but not altogether unprecedented in international law. The six individuals named above would be charged with war crimes - a well-defined crime under international, and most domestic laws. Many individuals have already been prosecuted for war crimes in other international tribunals, such as the ICTR, the ICTY, the Special Court for Sierra Leone, and most recently, the Cambodian Court (ECCC). Many individuals have already been prosecuted in domestic courts for war crimes, in the wake of either world wars or regime changes and transitions to democracy. Moreover, jurisdiction over defendants accused of war crimes can be, theoretically, easily justified in international law. So-called universal jurisdiction exists over war crimes, implying that any state can prosecute individuals accused of war crimes, even if the prosecuting state has no connection or nexus to the crime itself, to the victims or to the defendant. Furthermore, the so-called passive personality principle of jurisdiction would justify the Spanish exercise of jurisdiction over the above-named U.S. defendants, because this type of jurisdiction grants the state whose nationals the victims of the alleged crimes were the power to try defendants. In this case, some of the Guantanamo detainees were Spanish nationals; thus, under the passive personality principle, Spain would have the power to try the U.S. individuals accused of planning and installing the questionable regime applied at Guantanamo to the detainees.
As a policy and diplomacy matter, whether Spain should prosecute these individuals is a different issue. Some of the six individuals have already testified before the U.S. Congress over their alleged involvement in the mistreatment of Guantanamo detainees, and the issue of whether these individuals should be held accountable domestically (in the U.S.) is already being debated. Arguably, if some accountability mechanism is installed in the U.S., then Spain would have no business meddling into these allegations, at least from a policy and diplomacy perspective (as explained above, from a legal point of view, Spain does have the right and power to investigate and prosecute these individuals). If the U.S. decides not to hold any of these individuals accountable in any manner, then arguably Spain has more interests and incentives to investigate them. Whether its government will decide to pursue the investigation is doubtful - the German main prosecutor declined to investigate Donald Rumsfeld in 2004 over allegations of mistreatment of prisoners in the Abu Graib prison in Iraq, citing policy concerns. After all, the U.S. is an important potential ally and no country wants to alienate the American government.
I strongly believe that some kind of accountability is needed for the mistreatments that took place at Guantanamo, and I believe that some of the above-named individuals should be personally subjected to investigation and required to take responsibility. Preferably, this should take place within the U.S.; if it does not, then the only "punishment" these individuals will face is the fact that they will never again be able to vacation in Spain (or other European countries if they decide to agree with the Spanish decision to investigate), where they could potentially be arrested and prosecuted for war crimes. However inconvenient this may be for Bybee, Yoo, or others, I do not believe that it constitutes enough punishment for the serious mistreatments that took place at Guantanamo.