Yaser Esam Hamdi is a former American citizen who was captured in Afghanistan in 2001. The United States government claims that he was fighting with the Taliban against U.S. and Afghan Northern Alliance forces. He was declared an "illegal enemy combatant" by the Bush administration and detained for almost three years without charge. On October 9, 2004, on the condition that he renounce his U.S. citizenship and commit to travel prohibitions and other conditions, the government released him and deported him to Saudi Arabia, where he had been raised.

An unlawful combatant, illegal combatant or unprivileged combatant/belligerent is a person who directly engages in armed conflict in violation of the laws of war and therefore is claimed not to be protected by the Geneva Conventions. The International Committee of the Red Cross points out that the terms "unlawful combatant", "illegal combatant" or "unprivileged combatant/belligerent" are not defined in any international agreements. While the concept of an unlawful combatant is included in the Third Geneva Convention, the phrase itself does not appear in the document. Article 4 of the Third Geneva Convention does describe categories under which a person may be entitled to prisoner of war status. There are other international treaties that deny lawful combatant status for mercenaries and children.