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Australia
Practice Relating to Rule 37. Open Towns and Non-Defended Localities
Section C. Attacks on open towns and non-defended localities
Australia’s Defence Force Manual (1994) states: “Towns, villages, dwellings or buildings which are undefended are also protected from attack.” 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 534; see also § 732 (siege warfare).
With respect to non-defended localities, the manual states:
Military objectives within a non-defended locality, from which hostile acts are being conducted, can be attacked, subject to weapon and targeting considerations … Otherwise, non-defended localities cannot be attacked. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, §§ 726 and 732.
The manual further provides that “making non-defended localities … the object of attack” constitutes a grave breach or a serious war crime likely to warrant institution of criminal proceedings. 
Australia, Manual on Law of Armed Conflict, Australian Defence Force Publication, Operations Series, ADFP 37 – Interim Edition, 1994, § 1315(k); see also Law of Armed Conflict, Commanders’ Guide, Australian Defence Force Publication, Operations Series, ADFP 37 Supplement 1 – Interim Edition, 7 March 1994, § 1305(k).
Australia’s LOAC Manual (2006) states:
5.37 Towns, villages, dwellings or buildings which are undefended are also protected from attack …
Undefended localities
7.27 The attack or bombardment, by whatever means, of towns, villages, dwellings, or buildings which are undefended is prohibited. The reason for this rule is that there is no military need to attack a place that is not being defended. It can simply be occupied without resistance or bypassed. The concept of an undefended place does not apply to places in rear areas behind enemy lines. It applies only to places that are open to occupation by ground forces.
Non-defended locality
7.28 It is prohibited for parties to a conflict to attack, by any means whatsoever, non-defended localities.
Siege warfare
7.35 Attack on towns, villages, habitations or buildings that are undefended is prohibited unless they have become military objectives. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, §§ 5.37, 7.27, 7.28 and 7.35; see also §§ 9.24 and 9.43.
The manual also states:
[The 1977 Additional Protocol I] extends the definition of grave breaches to include the following … acts when committed wilfully, in violation of the relevant provisions of the protocol, and causing death or serious injury to body or health:
• making non-defended localities … the object of attack. 
Australia, The Manual of the Law of Armed Conflict, Australian Defence Doctrine Publication 06.4, Australian Defence Headquarters, 11 May 2006, § 13.26.
The LOAC Manual (2006) replaces both the Defence Force Manual (1994) and the Commanders’ Guide (1994).
Australia’s War Crimes Act (1945) considers “any war crime within the meaning of the instrument of appointment of the Board of Inquiry [set up to investigate war crimes committed by enemy subjects]” as a war crime, including the deliberate bombardment of undefended places. 
Australia, War Crimes Act, 1945, Section 3.
Australia’s Geneva Conventions Act (1957), as amended in 2002, provides: “A person who, in Australia or elsewhere, commits a grave breach … of [the 1977 Additional Protocol I] is guilty of an indictable offence.” 
Australia, Geneva Conventions Act, 1957, as amended in 2002, Section 7(1).
The grave breaches provisions in this Act were removed in 2002 and incorporated into the Criminal Code Act 1995.
Australia’s Criminal Code Act (1995), as amended to 2007, states with respect to serious war crimes that are committed in the course of an international armed conflict:
268.39 War crimeattacking undefended places
A person (the perpetrator) commits an offence if:
(a) the perpetrator attacks or bombards one or more towns, villages, dwellings or buildings; and
(b) the towns, villages, dwellings or buildings are open for unresisted occupation; and
(c) the towns, villages, dwellings or buildings do not constitute military objectives; and
(d) the perpetrator’s conduct takes place in the context of, and is associated with, an international armed conflict.
Penalty: Imprisonment for life. 
Australia, Criminal Code Act, 1995, as amended to 2007, Chapter 8, § 268.39, p. 328.
The Criminal Code Act states with respect to war crimes that are grave breaches of the 1977 Additional Protocol I:
268.98 War crimeattacking undefended places or demilitarized zones
A person (the perpetrator) commits an offence if:
(a) the perpetrator attacks one or more towns, villages, dwellings, buildings or demilitarized zones; and
(b) the towns, villages, dwellings or buildings are open for unresisted occupation; and
(c) the attack results in death or serious injury to body or health; and
(d) the perpetrator’s conduct takes place in the context of, and is associated with, an international armed conflict.
Penalty: Imprisonment for life. 
Australia, Criminal Code Act, 1995, as amended to 2007, Chapter 8, § 268.98, p. 371.
Australia’s ICC (Consequential Amendments) Act (2002) incorporates in the Criminal Code the war crimes defined in the 1998 ICC Statute, including “attacking undefended places” in international armed conflicts. 
Australia, ICC (Consequential Amendments) Act, 2002, Schedule 1, § 268.39; see also § 268.98 (grave breach of the 1977 Additional Protocol I).