Researching Other Sources of International Law

Customary Law: Non-State Resources / State Resources / General Principles of Law / Subsidiary Means

After treaties, the sources of international law mentioned in Art. 38(1) of the Statute of the International Court of Justice are: international custom, as evidence of a general practice accepted as law and the general principles of law recognized by civilized nations. Judicial decisions, international and national, and the teachings of the most highly qualified publicists of various nations are considered subsidiary means of determining international law.

This guide is an overview of research methods. For a list of specific sources and where they may be found see the Bibliography.


Customary Law

Establishing international custom is perhaps the most difficult task one can undertake in international law research. As a first step, you should probably start by gaining a good understanding of the concept of customary law. There are a number of useful books and articles on the theory of international custom, see the Bibliography. A particularly good discussion of researching customary law is Conducting Research in Customary International Law by Ralph F. Gaebler found in Contemporary Practice of Public International Law (1997) (Law Annex KZ1234 .C66 1997). There are other discussions of researching customary international law in the Bibliography.

International custom is derived from the historical actions of nations or state practice, as it is known. "[C]ustomary international law results from a general and consistent practice of states followed by them from a sense of legal obligation." Restatement of the Law Third, Foreign Relations of the United States § 102(2) (1987) (Law Reserve & Law Annex Ref KF 4651 R47 1987). This is also available on Westlaw and in Lexis in two library files: a rules file and a table of contents file.

In other words, first you must determine the general and uniform state practice, and then you must figure out if states considered themselves legally bound to behave that way. But figuring out state practice is not a simple process, nor one that anyone other than a scholar is generally able (or willing) to undertake. Most of us rely on secondary source materials to determine what is viewed by experts as being international custom.

Secondary sources, i.e., books and articles, can often be the best way to gain an overview for the topic of public international law you are researching. It will also be a useful first step in identifying primary source material you will want to look at. There are a few resources to mention in addition to what you can find in the general secondary source discussions that are specific to international law:

Another useful tool for gaining an overview of particular areas of public international law, as well as references to seminal works, is the Encyclopedia of Public International Law (Law Annex JX1226 E5 1981) which is currently being reissued in updated form (Law Annex Ref JX 1226 E5 1992). The Restatement also contains references to secondary source materials. For other sources of expert opinion of areas of international law that are customary see the Bibliography.

For those who are more ambitious, there are various sources of evidence of international custom and state practice. These can be broken down into two categories: non-state sources and state sources.


Non-State Sources

The articulation of international law by intergovernmental entities can be taken as evidence of an evolving consensus on international custom. For example, the Permanent Court of International Justice or the International Court of Justice's determinations of international custom have weight. These decisions of these two courts can be found:

  • Permanent Court of International Justice Publications: Series A, A/B, B (Law Annex KZ209 .P47 1996, KZ209 P48 1996, KZ209 P49 1996 and on HeinOnline)
  • Reports of Judgments, Advisory Opinions, and Orders/International Court of Justice (Law Annex JX1971.6 I54) also on Westlaw (INT-ICJ) and at the ICJ website.

Other tribunals may also have made statements on rules of customary international law. For a complete list of international tribunals and their decisions see the Bibliography.

The resolutions and declarations of intergovernmental organizations, especially the United Nations, can be evidence of an international custom. Particularly important are the votes and comments of particular countries in response to resolutions and declarations. See the Bibliography for more resources including the Repertory of Practice of United Nations Organs and the Repertoire of Security Council Practice, very helpful guides to the resolutions of those bodies.

You can use the UN Research Guide for more information about researching in the UN system. The single most helpful tool for researching UN documents is UNBISNet the UN catalog. It links you to full-text documents when they are online.

Finally, it is important to remember the movement to codify international law. The International Law Commission, in particular, has worked to codify international law. It holds annual sessions. The process of codification elicits a dialogue among states which can help clarify state practice. And there are several scholarly associations whose reports can be very helpful in tracking developments in particular areas. See the Bibliography for more information.


State Sources

State sources fall into two categories as well: (1) diplomatic materials, and (2) legal materials, like laws, court decisions, and administrative materials. Diplomatic materials are further subdivided into (1) materials relating to international law and (2) general diplomatic materials.

Materials relating to International Law

For the United States position on various issues of international law, The Department of State has also published the Digest of United States Practice in International Law (Law Annex JX 237 D54 and HeinOnline) articulating the United States position on various public international law issues. The Department of State has been publishing a supplement at its website. There is a quarterly supplement found in the American Journal of International Law (Law Annex, HeinOnline, Westlaw) called Contemporary Practice of the United States Relating to International Law. There are also several similar digests predating this most recent digest which began publication in 1973. See the Bibliography.

There are also yearbooks which publish articles about the practice of some countries in international law and often have a yearly digest. These can be found in searchable databases on HeinOnline and are also available in the library, see the Bibliography.

General Diplomatic Materials

There are many good sources of historical diplomatic papers. The Avalon Project at Yale Law School as an historical diplomatic documents database. Many of these resources, like Foreign Relations of the United States (Law Annex JX 233 A3, Avalon Project, HeinOnline and selected volumes at State Department website) are available in the library and covers the period from 1861-1968. Other countries have a similar collections of state papers, for example the British and Foreign State Papers (KD 4030 B7 1812-1968). The U.S. has many other sources of diplomatic practice which are listed in the Bibliography along with selected sources for other countries.

One of the more recent tools available to the researcher are the web sites for the various affairs offices of governments or their embassies. These may provide the actions and reactions of various governments in the international sphere. A word of caution: the web is a limited resource because it contains only recent materials for the most part - you can waste a lot of time looking for materials from earlier periods in foreign affairs.

Legislation and judicial decisions relevant to international obligations

This is essentially foreign law research. There are, however, a few sources that are specific to this kind of research like the American International Law Cases (Law Annex JX 238 A2 A44 ) which reprints cases from U.S. courts which have dealt with international obligations. There are other such resources listed in the Bibliography.


General Principles of Law

Determining the general principles which underlie the law of all nations is a task of comparative international law. There are several tools in this area, but again, it is one where using the existing work of scholars (as opposed to trying to figure it out for yourself) is probably the best way to go. See the Bibliography for books discussing this topic.

 


Subsidiary Means

The subsidiary means of determining international laws is through the decisions of international and national tribunals and through the writings of jurists. Many of these resources have been mentioned above because they are both evidence of customary international law and a subsidiary means of establishing customary international law.

There are many international tribunals aside from the ICJ and they are listed in the Bibliography.

Finding the writings of jurists has also been discussed above. The tricky part is figuring out who has enough of an international reputation to be considered an expert. The civil law systems have a long history of relying on the works of jurists to supplement legislation. Unlike he commonwealth jurisdictions, they have more faith in academics than in judges.

There are also international and national associations which are dedicated to the study of international law. Many of these have been operating for over a century and are a valuable source of expert opinion on international law. For a listing of some of these and their publications see the Bibliography.


 

Page maintained by Stefanie Weigmann
Last updated: September 2007