Related Rule
Australia
Practice Relating to Rule 5. Definition of Civilians
Australia’s Defence Force Manual (1994) states that a civilian is defined “in a negative fashion, namely, any person not belonging to the armed forces. The definition covers civilians collectively as well, when they are referred to as the ‘civilian population’.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 914.
Australia’s LOAC Manual (2006) states:
G. P. I [1977 Additional Protocol I] defines a civilian in a negative fashion, namely, any person not belonging to the armed forces. The definition covers civilians collectively as well, when they are referred to as the “civilian population”. In cases of doubt about civilian status, the benefit of the doubt is given to the person concerned. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 9.14; see also § 5.33.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).