Related Rule
United States of America
Practice Relating to Rule 147. Reprisals against Protected Objects
Section D. Objects indispensable to the survival of the civilian population
The US Operational Law Handbook (1993) provides:
The following measures are expressly prohibited by the law of war and are not excusable on the basis of military necessity:
m. Reprisals against … items such as food stuffs and livestock essential to the survival of the civilian population. 
United States, Operational Law Handbook, JA 422, Center for Law and Military Operations and International Law Division, The Judge Advocate General’s School, United States Army, Charlottesville, Virginia 22903-1781, 1993, p. Q-182.
In 1987, in submitting the 1977 Additional Protocol II to the US Senate for advice and consent to ratification, the US President announced his decision not to ratify the 1977 Additional Protocol I, stating, inter alia, that the Additional Protocol I “fails to improve substantially the compliance and verification mechanisms of the 1949 Geneva Conventions and eliminates an important sanction against violations of those Conventions”. 
United States, Message from the US President transmitting the 1977 Additional Protocol II to the US Senate for advice and consent to ratification, Treaty Doc. 100-2, 29 January 1987.
In 1987, the Deputy Legal Adviser of the US Department of State stated that the United States did not support “the prohibition on reprisals in article 51 of the 1977 Additional Protocol I and subsequent articles” and did not consider it part of customary law. 
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 Journal of International Law and Policy, Vol. 2, 1987, p. 426.
In its written statement submitted to the ICJ in the Nuclear Weapons case in 1995, the United States stated:
Various provisions of Additional Protocol I contain prohibitions on reprisals against specific types of persons or objects, including … objects indispensable to the survival of the civilian population (Article 54(4)) … These are among the new rules established by the Protocol that … do not apply to nuclear weapons. 
United States, Written statement submitted to the ICJ, Nuclear Weapons case, 20 June 1995, p. 31.