Ali Mussa Daqduq is a dangerous man. A senior operative with the Hezbollah terrorist organization, Mr. Daqduq has been held without charge by U.S. forces in Iraq for the past five years for helping to train militant Shiite militia members to carry out attacks against U.S. soldiers. One such attack claimed the lives of five U.S. service members.

But the United States may be forced to hand him over to Iraqi authorities before year’s end because of a security agreement signed during the Bush administration. The Obama administration must ensure that this does not happen.

The Iraqi government has a spotty track record in prosecutions, and inmates routinely escape from its shoddy prisons.  

But what to do with Mr. Daqduq if the administration maintains custody? Because Mr. Daqduq is an unlawful enemy combatant, the laws of war allow his detention until cessation of hostilities. But prosecution would be preferable, and a trial before a military commission appears to be the most obvious option.

Mr. Daqduq is alleged to have targeted military personnel in acts that violate the laws of war. The Military Commissions Act of 2009 allows prosecutions of unlawful enemy combatants, such as Mr. Daqduq, who engage in hostilities against the United States and its allies. 

Aversion to Guantanamo should not bar a military commission if it is the right venue for bringing Mr. Daqduq to justice. We, too, have called for Guantanamo’s closure. The detainee abuses and denial of basic legal rights there in the period immediately after the Sept. 11, 2001, attacks seriously damaged the country’s reputation. Yet much has changed since these abuses were first documented. 

The president should consider all options for dealing with Mr. Daqduq. Prosecution in a U.S. federal court should be weighed, as should detention under the laws of war. Most important, the facts and the law — and not politics — should dictate where Mr. Daqduq is held and tried.