Related Rule
Australia
Practice Relating to Rule 67. Inviolability of Parlementaires
Australia’s Commanders’ Guide (1994) provides: “The following examples constitute grave breaches or serious war crimes likely to warrant institution of criminal proceedings: … firing upon flags of truce.” 
Australia, Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 1305(q); see also § 840 (protection of cartel ships).
Australia’s Defence Force Manual (1994) states: “The following examples constitute grave breaches or serious war crimes likely to warrant institution of criminal proceedings: … firing upon flags of truce.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 1315(q); see also § 644 (protection of cartel ships).
The manual also provides: “An adversary displaying a white flag should be permitted the opportunity … to communicate a request for cease-fire or negotiation.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 910.
Australia’s LOAC Manual (2006) states: “An adversary displaying a white flag should be permitted the opportunity … to communicate a request for cease-fire or negotiation.” 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 9.10; see also §§ 6.44–6.45 and 8.49.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).