Conventional Assumptions. Andrew Hagen
asked a question in the comments to the recent Geneva Conventions post
that provides an opportunity to answer in line with one of the basic reasons for this blog: to look at some of the assumptions that underly commonly held positions, beliefs and opinions; and to address where those assumptions hold up well, and where they tend to go astray.
"But hasn't the US declared that it will follow the Geneva Convention as a matter of customary international law? Not sure about this."
The answer is yes or no, depending upon the assumptions behind the question.
There are two generalizations that seem to be fairly common assumptions. One generalization is a tendency to conflate "customary international law" with international agreements (treaties, conventions, protocols, etc.). The other is that the phrase "the Geneva Convention" has been popularized into a convenient label to refer to any of the Hague, Geneva and other international agreements that codify parts of the "Law of Armed Conflict" or the "Law of War" or "International Humanitarian Law."
Not that Andrew Hagen is necessarily working from either of those generalizations, but that they are quite common. His specific question actually seems to avoid the first; but, unless his use of the singular, "Convention," was a typo, the second generalization seems to fit.
Let's look at the Commander's Handbook on the Law of Naval Operations, NWP 1-14M, October 1995, "Chapter 5 - Principles and Sources of the Law of Armed Conflict."
5.4 SOURCES OF THE LAW OF ARMED CONFLICT
As is the case with international law generally, the principal sources of the law of armed conflict are custom, as reflected in the practice of nations, and international agreements.
5.4.1 Customary Law. The customary international law of armed conflict derives from the practice of military and naval forces in the field, at sea, and in the air during hostilities. When such a practice attains a degree of regularity and is accompanied by the general conviction among nations that behavior in conformity with that practice is obligatory, it can be said to have become a rule of customary law binding upon all nations. It is frequently difficult to determine the precise point in time at which a usage or practice of warfare evolves into a customary rule of law. In a period marked by rapid developments in technology, coupled with the broadening of the spectrum of conflict to encompass insurgencies and state-sponsored terrorism, it is not surprising that nations often disagree as to the precise content of an accepted practice of armed conflict and to its status as a rule of law. This lack of precision in the definition and interpretation of rules of customary law has been a principal motivation behind efforts to codify the law of armed conflict through written agreements (treaties and conventions.) However, the inherent flexibility of law built on custom and the fact that it reflects the actual--albeit constantly evolving--practice of nations, underscore the continuing importance of customary international law in the development of the law of armed conflict.
5.4.2 International Agreements. International agreements, whether denominated as treaties, conventions, or protocols, have played a major role in the development of the law of armed conflict. Whether codifying existing rules of customary law or creating new rules to govern future practice, international agreements are a source of the law of armed conflict. Rules of law established through international agreements are ordinarily binding only upon those nations that have ratified or adhered to them. Moreover, rules established through the treaty process are binding only to the extent required by the terms of the treaty itself as limited by the reservations, if any, that have accompanied its ratification or adherence by individual nations. Conversely, to the extent that such rules codify existing customary law or otherwise come, over time, to represent a general consensus among nations of their obligatory nature, they are binding upon party and non-party nations alike.
Principal among the international agreements reflecting the development and codification of the law of armed conflict are the Hague Regulations of 1907, the Gas Protocol of 1925, the Geneva Conventions of 1949 for the Protection of War Victims, the 1954 Hague Cultural Property Convention, the Biological Weapons Convention of 1972, and the Conventional Weapons Convention of 1980. Whereas the 1949 Geneva Conventions and the 1977 Protocols Additional thereto address, for the most part, the protection of victims of war, the Hague Regulations, the Geneva Gas Protocol, 1993 Chemical Weapons Convention, Hague Cultural Property Convention, Biological Weapons Convention, and the Conventional Weapons Convention are concerned, primarily, with controlling the means and methods of warfare. The most significant of these agreements (for purposes of this publication) are listed chronologically as follows:
1. 1907 Hague Convention Respecting the Laws and Customs of War on Land (Hague IV)
2. 1907 Hague Convention Respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land (Hague V)
3. 1907 Hague Convention Relative to the Laying of Automatic Submarine Contact Mines (Hague VIII)
4. 1907 Hague Convention Concerning Bombardment by Naval Forces in Time of War (Hague IX)
5. 1907 Hague Convention Relative to Certain Restrictions with Regard to the Exercise of the Right of Capture in Naval War (Hague XI)
6. 1907 Hague Convention Concerning the Rights and Duties of Neutral Powers in Naval War (Hague XIII)
7. 1925 Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous, or Other Gases, and of Bacteriological Methods of Warfare
8. 1936 London Protocol in Regard to the Operations of Submarines or Other War Vessels with Respect to Merchant Vessels (Part IV of the 1930 London Naval Treaty)
9. 1949 Geneva Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field*
10. 1949 Geneva Convention (II) for the Amelioration of the Condition of Wounded, Sick, and Shipwrecked Members of Armed Forces at Sea*
11. 1949 Geneva Convention (III) relative to the Treatment of Prisoners of War*
12. 1949 Geneva Convention (IV) relative to the Protection of Civilian Persons in Time of War*
13. 1954 Hague Convention for the Protection of Cultural Property in the event of armed conflict
14. 1972 Convention on the Prohibition of the Development, Production and Stockpiling of Bacteriological (Biological) and Toxin Weapons and on their Destruction
15. 1977 Protocol Additional to the Geneva Conventions of 1949 and Relating to the Protection of Victims of International Armed Conflict (Additional Protocol I)*
16. 1977 Protocol Additional to the Geneva Conventions of 1949 and Relating to the Protection of Victims of Non-International Armed Conflicts (Additional Protocol II)*
17. 1980 Convention on Prohibitions or Restrictions on the Use of Certain Conventional Weapons which may be Deemed to be Excessively Injurious or to have Indiscriminate Effects*
18. 1993 Convention on the Prohibition of Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction.
An asterisk (*) indicates that signature or ratification of the United States was subject to one or more reservations or understandings. The United States is a party to, and bound by, all of the foregoing conventions and protocols, except numbers 13, 15, 16 and 18. The United States has decided not to ratify number 15 (Additional Protocol I). The United States has ratified number 17, Protocols I and II, but has not ratified Protocol III.
[The full text of those 18 treaties, protocols and conventions, along with another 80, are available here
Customary law, then, is the greater or more universal law, binding upon everybody; while the international agreements are a lesser, multilateral law, only binding upon states that are parties to the agreement.
When "the Geneva Convention" (singular) is used as a convenient, general label, the question becomes, hasn't the US declared that it considers every international agreement related to warfare, even those to which it is neither a party or even a signatory, as binding customary international law? The answer to that question is, no.
When "the Geneva Convention" (singular) is used to refer to a specific 1949 convention (I - IV), the answer is, yes, for those four conventions.
If it refers to either of the 1977 Additional Protocols, the answer is, mostly yes. Where those Protocols overlap customary international law or other agreements the US has ratified and is bound by, the answer must be, yes. Where those Protocols extend new protections beyond customary international law, the answer is likely to be, yes, because of US policy regarding treaties. The US is a signatory to the protocols, which only obligates the US to consider ratifying them, they are not binding on a state until after ratification; however, it has generally been US policy to abide by treaties it has signed that have not yet been ratified, this has long been US policy and exceeds the requirements of Article 12 of the Vienna Convention on the Law of Treaties of 1969.
It was in keeping with that policy that Bush retracted the US signature from the Koyto Protocol and refused to sign the Rome Statute of the International Criminal Court, neither of which the US had any intentions of ratifying. Although the US has not, and probably will not, ratify either of the Additional Protocols, it is still listed as a signatory nation and the general US policy toward signed treaties applies in the absence of any specific national policy rejecting them.