Related Rule
United Kingdom of Great Britain and Northern Ireland
Practice Relating to Rule 32. Humanitarian Relief Objects
The UK LOAC Manual (2004) states in its chapter on maritime warfare:
13.33. The following classes of enemy vessels are exempt from attack:
c. vessels granted safe conduct by agreement between the belligerent parties including:
(2) vessels engaged in humanitarian missions, including vessels carrying supplies indispensable to the survival of the civilian population, and vessels engaged in relief actions and rescue operations
13.34. Vessels listed in paragraph 13.33 are exempt from attack only if they:
a. are innocently employed in their normal role;
b. submit to identification and inspection when required; and
c. do not intentionally hamper the movement of combatants and obey orders to stop or move out of the way when required. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 13.33–13.34.
With regard to internal armed conflict, the manual provides:
15.27. It is prohibited to attack the “personnel, installations, material, units or vehicles involved in a humanitarian assistance or peacekeeping mission in accordance with the Charter of the United Nations, so long as they are entitled to the protection given to civilians or civilian objects under the international law of armed conflict”.
15.27.1. The protection and delivery of relief supplies will usually be dealt with in agreements between the state concerned and the relief agencies in question. 
United Kingdom, The Manual of the Law of Armed Conflict, Ministry of Defence, 1 July 2004, §§ 15.27–15.27.1.
Under the UK ICC Act (2001), it is a punishable offence to commit a war crime as defined in Article 8(2)(b)(iii) and (e)(iii) 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 Report on UK Practice states: “As regards protection of relief personnel and objects, the United Kingdom has, both in words and in action, demonstrated support for this principle, as in Iraq, and in the former Yugoslavia.” 
Report on UK Practice, 1997, Chapter 4.2.