Some inmates were subjected to controversial interrogation techniques
Spain's attorney general has rejected an attempt to bring a criminal case against six former US officials over torture allegations at Guantanamo Bay.
The officials, including former US attorney general Alberto Gonzalez, were accused of giving a legal justification for torture at the US detention centre.
But Candido Conde-Pumpido said the case had "no merit" as they were not present when the alleged abuse took place.
Spanish courts can prosecute people for crimes committed outside Spain.
Using the principle of "universal justice", they have also investigated alleged crimes in Argentina, Tibet, El Salvador and Rwanda.
The Spanish judge, Baltasar Garzon, who is best known for issuing an arrest warrant for former Chilean military leader Augusto Pinochet in 1998, had requested the attorney general's advice last month on whether to investigate the six former US officials following a complaint from human-rights lawyers.
"We cannot support that action," Mr Conde-Pumpido told reporters.
"If one is dealing with a crime of mistreatment of prisoners of war, the complaint should go against those who physically carried it out."
He said a trial of the men would have turned Spain's National Court "into a plaything" to be used for political ends.
While saying his office supported the principal of universal justice, Mr Conde-Pumpido said that if there was a legitimate reason to file a complaint against the six accused, "it should be done before local courts with jurisdiction, in other words in the United States".
Correspondents say that while Mr Conde-Pumpido's recommendation reduces the chances of Judge Garzon launching an investigation, he could still do so anyway.
Gonzalo Boye, one of the lawyers who filed the complaint, said the decision was politically motivated and set a "terrible precedent".
"The attorney general speaks of the court being turned into a plaything. Well, I don't think the attorney-general's office should be turned into a plaything for politicians," he told the Associated Press news agency.
In addition to Mr Gonzales, the complaint named former Undersecretary of Defence Douglas Feith; former Vice-President Dick Cheney's chief of staff, David Addington; Justice Department officials John Yoo and Jay Bybee; and Pentagon lawyer William Haynes.
It is alleged the men advised former President George W Bush that he could ignore the Geneva Conventions, and provided legal cover to allow interrogators to use techniques such as "water-boarding".