What is international law?

What is international law?
The term “international law” conjures up many definitions (Carter, Oppenheim, Shaw). Generally, international law is a broad term to describe the legal mechanisms that govern relationships across boundaries; the choice of law when there are conflicts of law; and the implicit and explicit international norms requiring adherence under domestic laws. International law traditionally has beend divided broadly into two types: public international law and private international law.

Public international law, jus gentium publicum, governs the relationships among countries, among nongovernmental organizations, and among countries and nongovernmental organizations across boundaries. Some scholars limit the scope of public international law to UN treaties, the Geneva Conventions, and the Law of the Sea. For more information, a good treatise is Ian Brownlie, Principles of Public International Law (6th ed.).

Private international law, jus gentium privatum, is sometimes referred to as “conflicts of law” because it determines which set of laws apply to private transactions. It includes cross-border transactions and transnational law. Examples include contracts, divorces, child custody, and the recognition and enforcement of judgments in other countries.

Supranational law is an emergent category of international law by which states agree to limitations on their sovereignty in exchange for the benefits of cooperation in a supranational organization. The law of the European Union has been referred to as supranational law by some scholars. Similarly, the Eastern African Community may develop a supranational body of law. Some scholars feel that certain activities, such as the Internet and intellectual property, would be served better by the development of supranational law.

How is international law different from foreign law?
Foreign law largely refers to the body of law within one country, such as U.S. law, French law, or Chinese law. In contrast, international law refers to the collection of laws negotiated by governments or implicitly understood to be part of the customary legal framework. International law may require implementation or be expressed in the domestic laws of each country. Thus, the foreign law of any single state can include the implementation of international law. The study of the differences and similarities among the domestic laws of states is known as comparative law.

What are the sources of international law?
The three main sources of international law include: (1) Article 38 of the Statute of the International Court of Justice, (2) treaties and treaty interpretation, and (3) customary international law.

Note: In the United States, the 3rd Restatement of International Law produced by the American Law Institute is an influential, non-binding source.

(1) ICJ Article 38
ICJ Article 38 provides a list of sources of international law frequently used by other international courts and entities. Significantly, prior judicial decisions and learned scholars are “subsidiary means” for determining whether international law is binding and for interpreting the international legal obligation. Thus, the ICJ is not bound by case law precedent. Human rights courts similarly tend to focus on statutory text, treaties, and conventions, rather than precedent. Further, general comments and recommendations by commissions and committees may be treated with equal or greater weight than prior judicial decisions. Still, stare decisis, the doctrine under which courts adhere to precedent on questions of law, remains important because prior decisions reflect evidence of state practice and provide informative perspective on international custom and laws.

(2) What are the types of treaties and sources for treaty interpretation?
Treaties and other international agreements include bilateral agreements, regional agreements, and multilateral agreements. A self-executing treaty may be binding ex proprio vigore, or on its own, without additional domestic legislation. If an international agreement requires domestic legislation, the treaty is referred to as a non self-executing treaty.

The Vienna Convention on the Law of Treaties (VCLT), 23 May 1969, 1155 U.N.T.S. 331, entry into force 27 Jan. 1980, governs the enforcement of treaties. Treaties are legally binding upon states that ratify the treaty and upon the treaty’s entry into force. A state that ratifies a treaty is known as a “party” to the treaty and accepts all the obligations, subject to legitimate reservations, understandings, and declarations (RUDs). A signatory state is one that signs the treaty but has not yet ratified the treaty. A signatory state cannot act to defeat the object and purpose of the treaty but is not bound by the obligations of the treaty. Under Article 62 of the VCLT, a party may be able to modify or terminate a treaty due to an unforeseeable and fundamental change of circumstances. This principle does not apply to treaties defining geographical boundaries and cannot be invoked as the result of a breach of a treaty. (ICJ, Gabcikovo-Nagymaros Project, Hungary v. Slovakia (applying Article 62)).

For interpretation of treaties, courts unsurprisingly rely on the actual text of the treaty. Courts also may consider the travaux preparatoires, which is the legislative history of a treaty and the drafting documents of a treaty. Other sources include case law, commentaries, yearbooks, digests, and published collections on treaties.

(3) What is “customary” international law?
International law recognizes that not all law is codified or explicitly agreed to by states. Accordingly, international law supports state practice, also referred to as the behavior of states or state custom, and opinio juris as sources of international law. Although not objectively codified in treaties or international agreements, customary international law is legally binding upon states. For example, the Universal Declaration of Human Rights was a non-binding “declaration” by states of worthy goals and norms, yet parts of the UDHR have evolved into binding customary law. As you can imagine, states tend to disagree over whether a norm has become binding under customary law.

When is customary international law binding? The strongest tests for whether a state is bound under customary international law is whether the state intended to be bound or whether there was a violation of a jus cogens norm. Criteria used by international courts to determine the existence of a legally binding obligation under customary international law include: (a) the length of time, (b) the existence of constant and uniform usage, and (c) the general acceptance of the norm by the international community and other states.

Customary international law is not binding on persistent objector states. A state is not legally bound if it objected “persistently” to the norm or customary legal standard upon the formation of the norm and consistently thereafter. For example, the United States is a persistent objector to the prohibition of the death penalty.

Some important ICJ cases involving customary international law include:

What is “Jus Cogens”?
Jus cogens refers to universal peremptory norms, also sometimes called the “higher laws.” A jus cogens norm represents a norm from which no country may derogate. Further, no persistent objectors are allowed. If part of a treaty violates a jus cogens norm, then the entire treaty will be invalidated under VLCT Articles 53 and 64. Still, jus cogens prohibitions do not need to be codified to impose legally binding obligations on states or for enforcement. Generally, six types of crime rise to the level of jus cogens: genocide, crimes against humanity, war crimes, crimes of aggression, slavery, piracy, and torture. The first four are included in Article 5 of the Rome Statute of the International Criminal Court (ICC).

What are some general principles of international law?
Here are a few of the commonly encountered concepts for relations among countries:

1. Self-determination is the right of a nation or a peoples to determine their political outcome. Under international human rights law, the International Covenant on Civil and Political Rights (ICCPR) and the International Covenant on Economic, Social and Cultural Rights (ICESCR) recognize that “all peoples have the right of self-determination. By virtue of that right they freely determine their political status and freely pursue their economic, social and cultural development.”

2. Sovereignty. The Westphalian conceptualization of sovereignty focuses on territorial integrity and the exclusion of foreign actors in domestic affairs.

3. Comity is the principle by which the courts of one jurisdiction may consent to the laws or decisions of another. The comity of nations refers to the recognition accorded by one nation to the laws and institutions of another.

4. Reciprocity is the notion that states have rights and obligations towards each other than must be respected reciprocally.

When was the birth of international law?
The Peace of Westphalia in 1648, codified in two treaties, ended decades of horrendous wars in Europe and created the concept of the nation-state. A traditional nation-state has territoriality and sovereignty for actions within its borders. Yet, some scholars credit Nuremberg Trials with the beginning of international law; see the blog posting: Nuremberg: Birth of International Law. At minimum, Nuremberg marked a new age of international law to include constraints on sovereignty, individual liability for international crimes, and international human rights law.

Is international law really “law”?
Some scholars contend that international law is not “law” in the truest sense because there are no effective enforcement mechanisms. Because states voluntarily consent to be bound, sovereign states reserve the unilateral right to comply or not to comply. The decision to comply may be influenced by nuanced understandings of the costs of treaty ratification, the costs of compliance, and the likelihood of changing practices within the state. As a result, they argue, the voluntary compliance model is political in nature rather than juridical. They further argue that this lack of enforcement renders international law fundamentally different from binding domestic law.

• More International Law Background Fact Sheets
• International Law Terms / Glossary