Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 52. Pillage
The UK Military Manual (1958) states that pillage is prohibited whether in the territory of the parties to a conflict or in occupied territory. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 42.
The manual also provides: “Pillage of a town, even when it has been taken by assault, is forbidden.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 306.
In connection with the requirements for the granting to irregular combatants of the rights of the armed forces, the manual stipulates: “Irregular troops should have been warned against the employment of … pillage.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 95.
The manual also states: “In addition to the ‘grave breaches’ of the 1949 [Geneva] Conventions, … the following are examples of punishable violations of the laws of war, or war crimes: … pillage.” 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 626(j).
In respect of enemy private property, the manual further provides:
Private property must be respected. It must not be … pillaged, even if found in a captured town or other place. This prohibition embodied in the Hague Rules [1907 Hague Regulations] did not constitute a new rule. However, it has for a long time past been embodied in the regulations of every civilised army, for nothing is more demoralising to troops or more subversive of discipline than plundering. Theft and robbery are as punishable in war as in peace, and the soldier in an enemy country must observe the same respect for property as in his garrison at home. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 589.
The UK LOAC Pamphlet (1981) provides: “It is forbidden … to commit pillage, even if the town or place concerned is taken by assault”. 
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(d).
The manual lists the “Rules for soldiers”, including the following: “I must not – … take enemy property for my personal use.” 
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, Annex A, p. 44, § 6.
As a “rule for non-commissioned officers”, looting is also prohibited. 
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, Annex A, p. 46, § 8.
The UK LOAC Manual (2004) states: “Even if a town or place has been taken by assault, pillage is prohibited.” 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 5.35.
With regard to internal armed conflict, the manual states:
15.23. Pillaging a town or place, even when taken by assault, is forbidden.
15.23.1. Pillage, also known as plunder or looting, is the same as stealing, which is an offence in peace or war. It must be distinguished from the lawful requisitioning of property for military, rather than private, purposes. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 15.23–15.23.1.
In its chapter on enforcement of the law of armed conflict, the manual refers to “looting” as a war crime “traditionally recognized by the customary law of armed conflict”. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, § 16.29.
The UK Army Act (1955), as amended in 1971, provides:
Any person subject to military law who –
(b) steals any property which has been left exposed or unprotected in consequence of any such operations as are mentioned in paragraph (a) above [warlike operations], or
(c) takes otherwise than for the public service any vehicle, equipment or stores abandoned by the enemy,
shall be guilty of looting and liable, on conviction by court-martial, to imprisonment or any less punishment provided by this Act. 
United Kingdom, Army Act, 1955, as amended in 1971, Section 30(b) and (c).
The UK Air Force Act (1955), as amended in 1971, states:
Any person subject to air-force law who –
(b) steals any property which has been left exposed or unprotected in consequence of any such operations as are mentioned in paragraph (a) above [warlike operations], or
(c) takes otherwise than for the public service any vehicle, equipment or stores abandoned by the enemy,
shall be guilty of looting and liable, on conviction by court-martial, to imprisonment or any less punishment provided by this Act. 
United Kingdom, Air Force Act, 1955, as amended in 1971, Section 30(b) and (c).
Under the UK ICC Act (2001), it is a punishable offence to commit a war crime as defined in Article 8(2)(b)(xvi) and (e)(v) 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).
The UK Armed Forces Act (2006) states:
4 Looting
(1) A person within subsection (4) commits an offence if, without lawful excuse—
(a) he takes any property from a person who has been killed, injured, captured or detained in the course of an action or operation of any of Her Majesty’s forces or of any force co-operating with them; or
(b) he searches such a person with the intention of taking property from him.
(2) A person within subsection (4) commits an offence if, without lawful excuse—
(a) he takes any property which has been left exposed or unprotected in consequence of—
(i) an action or operation of any of Her Majesty’s forces or of any force co-operating with them; or
(ii) an event, or state of affairs, in relation to which such an action or operation is undertaken; or
(b) he searches any place or thing with the intention of taking property of a description mentioned in paragraph (a).
(3) A person within subsection (4) commits an offence if he takes otherwise than for the public service any vehicle, equipment or stores abandoned by an enemy.
(4) A person is within this subsection if he is—
(a) a person subject to service law; or
(b) a civilian subject to service discipline. 
United Kingdom, Armed Forces Act (2006), Section 4.
In 1990, during a debate in the UN Security Council relating to the Iraqi invasion of Kuwait, the United Kingdom condemned acts of pillage committed by Iraq. 
United Kingdom, Statement before the UN Security Council, UN Doc. S/PV.2962, 28 November 1990, pp. 3–6.
A training video on IHL produced by the UK Ministry of Defence states unequivocally that “pillage is forbidden”. 
United Kingdom, Ministry of Defence, Training Video: The Geneva Conventions, 1986, Report on UK Practice, 1997, Chapter 2.3.
The Report on UK Practice refers to a letter from a UK army lawyer which noted:
The current view seems to be that units may lawfully seize enemy property on the battlefield and retain it as booty, but individuals doing the same run the risk of being charged with looting. Retention by units and formations of booty is subject to approval by Government whereas appropriation of property by individuals on the battlefield is strictly illegal.  
Report on UK Practice, 1997, Letter from an army lawyer, 24 February 1998, Answers to additional questions on Chapter 2.3.
[emphasis in original]
The UK Military Manual (1958) states:
A special class of war crime is that sometimes known as “marauding”. This consists of ranging over battlefields and following advancing or retreating armies in quest of loot, robbing … stragglers and wounded and plundering the dead – all acts done not as a means of carrying on the war but for private gain. Nevertheless, such acts are treated as violations of the law of war. Those who commit them, whether civilians who have never been lawful combatants, or persons who have belonged to a military unit, an organised resistance movement or a levée en masse, and have deserted and so ceased to be lawful combatants, are liable to be punished as war criminals. They may be tried and sentenced by the courts of either belligerent. 
United Kingdom, The Law of War on Land being Part III of the Manual of Military Law, The War Office, HMSO, 1958, § 636.