The 220-page suit was sent to federal prosecutors by U.S. and German attorneys under a German law that allows the prosecution of war crimes regardless of where they were committed. It alleges that Rumsfeld personally ordered and condoned torture.
"One of the goals has been to say a torturer is someone who cannot be given a safe haven," said Michael Ratner, the president of New York's Center for Constitutional Rights, which is behind the litigation.
"It sends a strong message that this is not acceptable."
The suit is brought on behalf of 12 alleged torture victims — 11 Iraqis held at Baghdad's Abu Ghraib prison and Mohamad al-Qahtani, a Saudi being held at the U.S. military prison in Guantanamo Bay, Cuba, who has been identified by the United States as a would-be participant in the Sept. 11 attacks.
Captured in December 2001 along the Afghanistan-Pakistan border, al-Qahtani would not crack under normal questioning, so Rumsfeld approved harsher methods, according to testimony before U.S. Congress.
After FBI agents raised concerns, military investigators began reviewing the case and in July 2005 said they confirmed abusive and degrading treatment that included forcing al-Qahtani to wear a bra, dance with another man, stand naked in front of women and behave like a dog. Still, the Pentagon determined "no torture occurred."
German prosecutors already declined to investigate a more limited suit in 2004, arguing that it was up to the United States to hold any inquiry and that there were no indications U.S. authorities or courts would refrain from doing so.
The attorneys involved think they have a better case this time, armed with documents from 2005 congressional hearings on the al-Qahtani case. They argue that Rumsfeld's resignation last week means prosecutors may be under less political pressure to shun the case.
They also have former U.S. Army Brig. Gen. Janis Karpinski, the one-time commander of all U.S. military prisons in Iraq, as a witness on their behalf.
Karpinski, who was relieved of her command and demoted to colonel last year, says she did not know about prisoner abuse and asserts that higher-ups encouraged cruel treatment.
"It was done incrementally over time to prevent people from seeing what was actually approved and permitted," Karpinski said at a news conference alongside the lawyers backing the case. "It certainly escaped my perception ... when they thought that Janis Karpinski was getting too close to uncovering this information or these events, they took me out of the equation."
Pentagon spokeswoman Cynthia Smith and Frank Wallenta, spokesman for German federal prosecutors, both said they could not comment because they had not yet received the suit in their offices.
In addition to Rumsfeld, the suit names U.S. Attorney General Alberto Gonzales, former CIA director George Tenet, former commander of all U.S. forces in Iraq Lt. Gen. Ricardo Sanchez and eight others, alleging that they either ordered, aided, or failed to prevent war crimes.
A case could not be brought with the International Criminal Court, because the United States is not a member, Ratner said, and could not be pursued through the U.N. because the U.S. has veto power.
Wolfgang Kaleck, the German attorney who is leading the litigation, said the suit's backers would appeal if prosecutors refuse to take up the case, and raised the prospect of further attempts in other European countries.