Related Rule
Australia
Practice Relating to Rule 3. Definition of Combatants
Australia’s Defence Force Manual (1994) provides: “Combatants comprise all organised armed forces, groups and units (except medical service and religious personnel).” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 512; see also Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, Glossary, p. xxi.
Australia’s LOAC Manual (2006) states:
Combatants comprise all organised armed forces, groups and units (except medical service and religious personnel) which are under the command of a party to a conflict and are subject to an internal disciplinary system, which enforces compliance with the LOAC. Where persons are not members of armed forces, they must also have a fixed distinctive sign recognisable at a distance and carry arms openly. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 5.12.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).