Related Rule
Australia
Practice Relating to Rule 23. Location of Military Objectives outside Densely Populated Areas
Australia’s Defence Force Manual (1994) states:
Defences and defensive positions should also be sited, if practicable, to avoid or minimise collateral damage. Ideally, all military objectives, including defensive positions, should be sited outside heavily populated areas. As in offensive operations, where a location or object may be equally successfully defended from any one of several defensive positions, LOAC requires that the defence should be conducted from the position which would cause the least danger to civilians and civilian objects. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 553.
The manual requires commanders to refrain from “locating military objectives within or near densely-populated areas”. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 556(b).
Australia’s LOAC Manual (2006) states:
Defences and defensive positions should also be sited, if practicable, to avoid or minimise collateral damage. Ideally, all military objectives, including defensive positions, should be sited outside heavily populated areas. As in offensive operations, where a location or object may be equally successfully defended from any one of several defensive positions, the LOAC requires that the defence should be conducted from the position which would cause the least danger to civilians and civilian objects. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 5.58.
The manual also requires commanders to refrain from “locating military objectives within or near densely-populated areas”. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 5.61.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).