Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 52. Pillage
Section B. Pillage committed by civilians
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.