Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 54. Attacks against Objects Indispensable to the Survival of the Civilian Population
The UK LOAC Pamphlet (1981) provides: “It is forbidden … to direct attacks at objects indispensable to the survival of the civilian population such as foodstuffs, crops, livestock and drinking water.” 
United Kingdom, The Law of Armed Conflict, D/DAT/13/35/66, Army Code 71130 (Revised 1981), Ministry of Defence, prepared under the Direction of The Chief of the General Staff, 1981, Section 4, p. 14, § 5(g).
According to the UK LOAC Manual (2004), it is prohibited
to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population, such as foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works, for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive, whether in order to starve out civilians, to cause them to move away, or for any other motive. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.27.
The manual further provides:
Extensive destruction not justified by military necessity, particularly of things indispensable to the survival of the civilian population (including food, agricultural areas, drinking water installations, irrigation works and the natural environment) with a view to denying them to the civilian population or the adverse party is prohibited and may amount to a grave breach. … The cumulative effect of this is to ban the type of general destruction known as a “scorched earth policy” in occupied territory. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 11.91 11 –11.91.1.
In its chapter on air operations, the manual states: “Air bombardment must not destroy or render useless objects indispensable to the survival of the civilian population.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 12.26.
With regard to internal armed conflict, the manual states:
15.19. Starvation of civilians as a method of warfare is prohibited.
15.19.1. The right to life is a non-derogable human right. Violence to the life and person of civilians is prohibited, whatever method is adopted to achieve it. It follows that the destruction of crops, foodstuffs and water sources, to such an extent that starvation is likely to follow, is also prohibited. The same applies to sieges, blockades, embargoes, or the blocking of relief supplies with the intention of causing starvation. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 15.19–15.19.1.
Under the UK ICC Act (2001), it is a punishable offence to commit a war crime as defined in Article 8(2)(b)(xxv) of the 1998 ICC Statute. 
United Kingdom, ICC Act, 2001, Sections 50(1) and 51(1) (England and Wales) and Section 58(1) (Northern Ireland).
At the CDDH, the United Kingdom sponsored a draft article on the prohibition of starvation which contained the rule that it is “forbidden to attack, destroy, remove or render useless, crops, drinking water supplies, irrigation works, livestock, foodstuffs or food producing areas for the purpose of denying them to the enemy or the civilian population”. 
United Kingdom, Proposal of amendment to Article 48 of the draft Additional Protocol I submitted to the CDDH, Official Records, Vol. III, CDDH/III/67, 19 March 1974, p. 218, § 2.
The United Kingdom favoured an exhaustive list of objects considered indispensable to the survival of the civilian population instead of an illustrative list “to achieve greater clarity”. 
United Kingdom, Statement at the CDDH, Official Records, Vol. XIV, CDDH/III/SR.16, 19 March 1974, p. 139, § 56; see also Statement at the CDDH, Official Records, Vol. IV, CDDH/III/SR.17, 19 March 1974, p. 148, § 31.
Upon ratification of the 1977 Additional Protocol I, the United Kingdom stated that it “understands that paragraph 2 [of Article 54] has no application to attacks that are carried out for a specific purpose other than denying sustenance to the civilian population or the adverse party”. 
United Kingdom, Reservations and declarations made upon ratification of the 1977 Additional Protocol I, 28 January 1998, § l.
The UK LOAC Manual (2004) states:
Military action may only be taken for the purpose of attacking, destroying, removing or rendering useless “foodstuffs, agricultural areas for the production of foodstuffs, crops, livestock, drinking water installations and supplies and irrigation works” if they are used by an adverse party:
a. “as sustenance solely for the members of its armed forces”; or
b. “if not as sustenance, then in direct support of military action”.
In the latter case, no action may be taken against these objects if it “may be expected to leave the civilian population with such inadequate food or water as to cause its starvation or force its movement”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.19.
The UK LOAC Manual (2004) states:
In cases of imperative military necessity, a party to the conflict may depart from the prohibition relating to indispensable objects in order to defend its national territory from invasion, but only in those parts of its territory that are under its control. The exception for the defence of national territory might include, for example, the flooding of low-lying areas to impede invading forces. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.19.