Related Rule
Israel
Practice Relating to Rule 108. Mercenaries
Israel’s Manual on the Laws of War (1998) states:
Another provision in the Additional Protocols is meant precisely to deny prisoner-of-war status to … mercenaries. This provision, which was adopted under pressure from African countries, is accepted as a customary rule and is therefore binding. 
Israel, Laws of War in the Battlefield, Manual, Military Advocate General Headquarters, Military School, 1998, p. 51.
Israel’s Manual on the Rules of Warfare (2006) states:
[A] provision in the Additional Protocols actually denies the status of prisoner-of-war from a different category of combatant, that of a mercenary. This provision, which was passed through pressure from the African nations, has been accepted as a customary provision and is therefore binding. 
Israel, Rules of Warfare on the Battlefield, Military Advocate-General’s Corps Command, IDF School of Military Law, Second Edition, 2006, p. 33.
The Manual on the Rules of Warfare (2006) is a second edition of the Manual on the Laws of War (1998).