The case had received widespread attention after Republican lawmakers demanded that Daqduq, a Lebanese national, be taken to the military detention center at Guantanamo Bay, Cuba.
On Friday, Sens. John McCain (R-Ariz.), Mitch McConnell (R-Ky.), Joseph I. Lieberman (I-Conn.) and Lindsey O. Graham (R-S.C.) called the transfer “disgraceful” in a statement that also said the administration had failed to “exercise our influence effectively with the Iraqi government to ensure that a committed killer of Americans would be held accountable for his crimes in the U.S. system of justice.”
The Obama administration had explored the possibility of charging Daqduq in a military commission to be held in the United States. But officials said they had no choice but to transfer him to Iraqi custody under the terms of the security agreement negotiated in 2008 by the George W. Bush administration, which requires all U.S. troops to leave Iraq by Dec. 31 and the consent of the Iraqi government to transfer individuals into or out of the country.
The government of Prime Minister Nouri al-Maliki refused to allow the United States to take Daqduq, and the Obama administration decided not to whisk him out of the country secretly as some on Capitol Hill had urged.
“It would destroy our relationship with Iraq at a time when we are entering a new chapter,” an administration official said about the possibility of rendering Daqduq to a trial in the United States. The official spoke on the condition of anonymity to discuss sensitive internal deliberations.
Sami al-Askari, a lawmaker and close aide to Maliki, said Daqduq had been transferred to the Iraqi Justice Ministry, which would investigate whether there was enough evidence to charge him with crimes. He said he thought the U.S. military had also handed over whatever evidence it had connecting Daqduq to the killings.
However, Askari said, the U.S. military had told the Iraqi government in the past that it could not share evidence related to Daqduq because it included sensitive intelligence. In 2010, a senior U.S. military official said the military did not have the kind of evidence that could be used to charge Daqduq in an Iraqi court.
An administration official said that the possibility of a U.S. trial was not closed and that if the Iraqis decide they cannot prosecute Daqduq, the administration could reopen talks on transferring him to the United States.
The five American soldiers were killed during a raid on the offices of a provincial council in Iraq by a Shiite militant group, Asaib al-Haq, which the U.S. military said had been advised and trained by Daqduq. He was detained in March 2007, and the U.S. military said he admitted that he was asked to go to Iraq by Iranian officials to train Shiite militants.
Two leading members of the group, brothers Qais and Laith Khazali, also were detained in connection with the attack. They were released after negotiations with the Iraqi government aimed, in part, at bringing Asaib al-Haq into the political process.
U.S. military officials say the group has continued to stage attacks against American troops throughout the remainder of their stay in Iraq, including at least one roadside bombing against departing soldiers a month ago. The Khazali brothers are living in Iran.
Finn reported from Washington.