Related Rule
United States of America
Practice Relating to Rule 55. Access for Humanitarian Relief to Civilians in Need
The US Field Manual (1976) provides:
Each High Contracting Party shall allow the free passage of all consignments of medical and hospital stores and objects necessary for religious worship intended only for civilians of another High Contracting Party, even if the latter is its adversary. It shall likewise permit the free passage of all consignments of essential foodstuffs, clothing and tonics intended for children under fifteen, expectant mothers and maternity cases.
The obligation of a High Contracting Party to allow the free passage of the consignments indicated in the preceding paragraph is subject to the condition that this Party is satisfied that there are no serious reasons for fearing:
(a) that the consignments may be diverted from their destination,
(b) that the control may not be effective, or
(c) that a definite advantage may accrue to the military efforts or economy of the enemy through the substitution of the above-mentioned consignments for goods which would otherwise be provided by the enemy or through the release of such material, services or facilities as would otherwise be required for the production of such goods. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 262.
With regard to occupying powers, the manual states:
If the whole or part of an occupied territory is inadequately supplied, the Occupying Power shall agree to relief schemes on behalf of the … population, and shall facilitate them by all the means at its disposal.
Such schemes … shall consist, in particular, of the provision of the consignments of foodstuffs, medical supplies and clothing. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 388.
The manual also provides that the ICRC, the National Red Cross (or equivalent) Society or any other organization that may assist protected persons “shall be granted all facilities for [assisting protected persons] by the authorities, within the bounds set by military or security considerations”. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 269.
The US Naval Handbook (2007) states: “The [1949] Geneva Conventions recognize the special status of the ICRC and have assigned specific tasks for it to perform, including … providing relief to the civilian population of occupied territories.” 
United States, The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCWP 5-12.1/COMDTPUB P5800.7, issued by the Department of the Navy, Office of the Chief of Naval Operations and Headquarters, US Marine Corps, and Department of Homeland Security, US Coast Guard, July 2007, § 6.2.2.
In submitting the 1977 Additional Protocol II to the Senate for advice and consent to ratification, the US President, commenting on Article 18 of the Protocol, stated: “The parties to a conflict have a duty not to refuse passage of relief supplies for arbitrary reasons.” 
United States, Message from the US President Transmitting the 1977 Additional Protocol II to the Senate for advice and consent to ratification, Treaty Doc. 100-2, 29 January 1987, Comment on Article 18.
In 1987, the Deputy Legal Adviser of the US Department of State affirmed:
We support the principle … subject to the requirements of imperative military necessity, that impartial relief actions necessary for the survival of the civilian population be permitted and encouraged …
We support the principle … that the ICRC and the relevant Red Cross or Red Crescent organizations be granted all necessary facilities and access to enable them to carry out their humanitarian functions. 
United States, Remarks of Michael J. Matheson, Deputy Legal Adviser, US Department of State, The Sixth Annual American Red Cross-Washington College of Law Conference on International Humanitarian Law: A Workshop on Customary International Law and the 1977 Protocols Additional to the 1949 Geneva Conventions, American University Journal of International Law and Policy, Vol. 2, 1987, pp. 426 and 428.
According to the Report on US Practice, it is the opinio juris of the United States that:
Special agreements are necessary in order for relief personnel and vehicles to pass through military lines or receive special protection. It is a violation of international humanitarian law to deny conclusion of such agreements for arbitrary reasons …
Some conditions which the US government would not regard as arbitrary may be inferred from legislation dealing with relief shipments from the United States to regions of conflict. These include adequate procedures to ensure that the relief actually reaches the persons for whom it is intended, and any condition necessary to ensure the safety of the armed forces in combat. 
Report on US Practice, 1997, Chapter 4.2.
The US Field Manual (1956) provides:
If the whole or part of the population of an occupied territory is inadequately supplied, the Occupying Power shall agree to relief schemes on behalf of the said population, and shall facilitate them by all the means at its disposal.
Such schemes, which may be undertaken … by States shall consist, in particular, of the provision of consignments of foodstuffs, medical supplies and clothing.
All Contracting Parties shall permit the free passage of these consignments and shall guarantee their protection. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 388.
The US Field Manual (1956) provides:
Protected persons shall have every facility for making application to the Protecting Powers, the International Committee of the Red Cross, the National Red Cross (Red Crescent, Red Lion and Sun) Society of the country where they may be, as well as to any organization that might assist them. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 269.
The US Air Force Pamphlet (1956) states:
Article 30 [of the 1949 Geneva Convention IV] seeks to put teeth into the Geneva protections by requiring the parties to give protected persons every facility for making application to the Protecting Powers, the International Committee of the Red Cross, the National Red Cross (Red Crescent, Red Lion and Sun) Society of the country where they may be, as well as to any organization that might assist them. 
United States, Field Manual 27-10, The Law of Land Warfare, US Department of the Army, 18 July 1956, as modified by Change No. 1, 15 July 1976, § 14-4.