I can tell you from my own first-hand knowledge that some number of "U.S. security contractors" operating in both Afghanistan and Iraq would not be considered lawful combatants, either.
"4. Persons who accompany the armed forces without actually being members thereof, such as civilian members of military aircraft crews, war correspondents, supply contractors, members of labour units or of services responsible for the welfare of the armed forces, provided that they have received authorization from the armed forces which they accompany, who shall provide them for that purpose with an identity card similar to the annexed model. "
http://www.unhchr.ch/html/menu3/b/91.htm