Enemy combatant was the term preferred, by the George W. Bush Administration, for members of al-Qaeda, Taliban, and others it considered ineligible for prisoner of war status. The more common language is "unlawful combatant", a lawful combatant meeting the criteria, adjudicated by a "competent tribunal" if necessary, for POW eligibility. The term has been explictly rejected by the Obama Administration.
On February 7, 2002, George W. Bush wrote
"I determined.... that members of al Qaeda, the Taliban, and associated forces are unlawful enemy combatants who are not entitled to the protections that the Third Geneva Convention provides to prisoners of war." 
The critical criteria for lawful combatant status are, according to the Third Geneva Convention:
- Being commanded by a person responsible for his subordinates;
- Having a fixed distinctive sign recognizable at a distance;
- Carrying arms openly;
- That of conducting their operations in accordance with the laws and customs of war
It was reasonably clear that al-Qaeda did not operate under these rules, although the situation was less clear for Taliban in Afghanistan.
- Nedra Pickler (March 13, 2009), "Obama admin. to end use of term 'enemy combatant'", Associated Press
- George W. Bush (July 20, 2007), Interpretation of the Geneva Conventions Common Article 3 as Applied to a Program of Detention and Interrogation Operated by the Central Intelligence Agency, Executive Order 13440
- Diplomatic Conference for the Establishment of International Conventions for the Protection of Victims of War, held in Geneva from 21 April to 12 August, 1949 (12 August 1949), Geneva Convention relative to the Treatment of Prisoners of War, U.N. High Commissioner for Human Rights