United States of America
Practice Relating to Rule 55. Access for Humanitarian Relief to Civilians in Need
Section A. Access for humanitarian relief
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.
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.
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”.
The US Naval Handbook (2007) states: “The  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.”
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.”
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.
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.