Unresolved questions are likely to touch off new criticism of Bush's conduct of the unpopular Iraq war, especially given the broad definition of unlawful combatants the president has used in justifying his detention policies at Guantanamo Bay, Cuba.
The issues surrounding the private security contractors are being examined by lawyers at the departments of State, Defense and Justice. Disagreements about the contractors' status exist between agencies and within the Pentagon itself.
"I think it is an unresolved issue that needs to be addressed," said a senior Defense Department official who spoke on condition of anonymity because he was not authorized to discuss the subject. "But if that is in fact the case, what the heck are we doing?"
The use of private contractors by the U.S. military and governments worldwide began long before the U.S invasions of Afghanistan and Iraq, but it has mushroomed in recent years. With relatively little controversy, contractors have assumed a greater share of support and logistics duties traditionally handled by uniformed military, such as protecting diplomats inside a war zone.
On Sept. 16, a Blackwater USA security team guarding U.S. diplomats was involved in a shooting that killed as many as 17 Iraqis. Blackwater said its personnel were under attack, but Iraqis said the team began the shooting.
Other incidents portraying the private guards as aggressive and heavily armed have since come to light.
The guards also operate under immunity from Iraqi law -- immunity was granted in 2004 by U.S. officials -- and in a murky status with respect to American laws.
The designation of lawful and unlawful combatants is set out in the Geneva Convention.Lawful combatants are nonmilitary personnel who operate under their military's chain of command. Others may carry weapons in a war zone but may not use offensive force. Under the international agreements, they may only defend themselves.
The amount of force being used in Iraq by security firms like Blackwater has raised questions.
The United States already has faced international criticism about its interrogation techniques and detention procedures, and charges that such practices do not adhere to international treaties. It was the government lawyers involved in those matters who first raised questions about the legal status of the private security contractors under Geneva Convention provisions.
But there is debate among those studying the question. Lawyers at the Justice Department are skeptical that the contractors could be considered unlawful combatants, but some in the State and Defense departments think the contractors in Iraq could be vulnerable to claims that their actions make them unlawful combatants.
If so, some experts say, the U.S. would have to pull them out of the war zone.
Legal experts widely agree that private contractors are allowed to use force to defend themselves. But the threshold between defensive and offensive force is ill-defined.
"In terms of these private military contractors, it really is, legally speaking, very convoluted," said the senior Defense official. "It is always true that people can defend themselves. The question then becomes: At what point does a contractor who is providing defensive security go beyond that?"
Interpretations also vary in academic circles, where the issue has been the subject of articles and discussions.
For a guard who is only allowed to use defensive force, killing civilians violates the law of war, said Michael N. Schmitt, a professor of international law at the Naval War College and a former Air Force lawyer. "It is a war crime to kill civilians unlawfully in an armed conflict," he said.
