Some inmates were subjected to controversial interrogation techniques
Spanish judges have agreed to consider charging six former US officials with providing legal justification for alleged torture at Guantanamo Bay.
Human rights lawyers brought the case against the six, who all served under former President George W Bush.
Among those named was former defence official Douglas Feith, who said the charges against him "made no sense".
Spanish courts can prosecute offences such as torture or war crimes even if they occurred in other countries.
The former officials - who include ex-Attorney-General Alberto Gonzalez - could face arrest on leaving the US if the courts decide to issue warrants.
The lawyers who brought the case accuse the six of providing legal cover to allow the security services to use techniques of interrogation such as "waterboarding".
They say the methods amounted to torture.
Mr Feith, a former under-secretary for defence, rebuffed the accusations.
"The charges as related to me make no sense," he said.
"They criticise me for promoting a controversial position that I never advocated."
The lawyers took their accusations to Judge Baltasar Garzon, who agreed to allow state prosecutors to decide if the case has merit.
Judge Garzon was responsible for bringing a prosecution against former Chilean leader Augusto Pinochet, who was arrested in the UK in 1998.
Spain's courts have also launched investigations over alleged crimes in Argentina, Tibet, El Salvador and Rwanda.