International Law

International law, or public international law, refers to both treaties and conventions and rules of customary international law that govern relations between states and interactions between states and various nonstate actors.  (Public international law is contrasted with private international law, which applies to relationships between private entities from different national jurisdictions.)  Like domestic law, public international law is defined by several sources, including treaties (agreements between states), conventions (equivalent to treaties) and common practices embodied in customary international law.  Public international law is generally binding only on states and recognized international organizations like the United Nations, which are in turn responsible for ensuring that they themselves, or their citizens or subjects, comply.  In some cases, however, international law applies to individuals as well.  International human rights law protects the rights of individuals, while the body of international criminal law applies to individuals’ criminal responsibility for violations of international laws like the Convention on the Prevention and Punishment of Genocide and the Convention Against Torture.

Sources of International Law

Treaties and Conventions:  The principal sources of statutory international law are international treaties and conventions.  Treaties are commonly defined as legally binding, written agreements concluded between states.  Conventions are treaties entered into by many states that, once ratified, become binding legal obligations on all signatory states.  For example, a convention such as the Rome Statute of the International Criminal Court conveys rights and obligations on all participant members to prosecute serious international crimes in accordance with its provisions.  Treaties are generally more limited in scope than conventions and often apply to a relationship between two states (bilateral treaties, such as an extradition agreement between the United States and Mexico) or a small group of states (e.g., the NATO Treaty, which binds its 28 members to common security arrangements).  Protocols have the same legal force as treaties and conventions but are supplemental to an existing treaty or convention, as in the Kyoto Protocol extending and modifying the existing United Nations Framework Convention on Climate Change (UNFCCC).  States that have agreed to be bound by an international agreement are then obliged to perform the duties of the accord in good faith according to standards of international law, while non signatories are expected not to impede the operation of a duly ratified international agreement.

Customary Law:  If conventions and treaties represent international statutory law, then the actions of states and decisions taken by international bodies such as the United Nations, the International Court of Justice and others may contribute to international common law, or customary international law.  There is often considerable debate among international lawyers about what constitutes customary international law and when a certain principle becomes binding on the community of nations.  But over time, certain principles of action among states become established as binding international norms – such as the prohibition on unprovoked state aggression, the outlawing of piracy or the need to provide defendants with access to the evidence that forms the basis of their accusation.  Generally, customary international law must be supported by the “settled practice” among states and by opinio juris, or the “belief that [a] practice is rendered obligatory by the existence of a rule of law requiring it.”  In other words, states must consistently act in a certain way and do so in the belief that they are obligated to act this way for a practice to attain the status of customary international law.  Given the uncertainties involved in such a calculation, in many cases treaties will act to codify what is already seen as customary international law to aid in its applicability or interpretation.

General Principles:  A third source of international law is the general principles common to a majority of legal systems around the world.  Thus, in the absence of a clear treaty provision or consistent behavior on the international level by states, international courts (as well as courts within states) may resort to general principles of law derived from the individual decisions of other jurisdictions.  For example, the U.S. Supreme Court may cite a decision by the European Court of Human Rights as evidence of an international legal principle that it recognizes and applies in the United States; see, for example, Lawrence v. Texas 539 U.S. 558 (2003) regarding non discrimination on the basis of sexual orientation.  A court may also choose to consider the views of scholarly writings or reports on general international legal principles to formulate its opinion of a discrete area of international law.


Subjects of International Law

Several distinct fields or divisions exist within the body of public international law.  In addition to the laws governing interactions among states and between states and international organizations, specific international laws address environmental and territorial issues, rules of armed conflict, human rights, criminal behavior and the like.  Below are some brief descriptions of significant subjects of public international law.

State-to-State Relations

Within the realm of state-to-state relations, public international law governs states’ sovereign rights as well as their obligations with respect to property, territory and commercial relations.  Fundamental interstate obligations are set out in a number of agreements, most importantly the Charter of the United Nations, which recognizes a member’s sovereign rights, establishes the principle of nonviolability of international borders and calls for the peaceful settlement of disputes.  The Vienna Convention on the Law of Treaties codifies the customary international law concerning state-to-state agreements, while the Vienna Conventions on Diplomatic Relations and on Consular Relations describe the basic rules for the conduct of diplomacy among states.  Ultimately, compliance with international law among states relies on states’ own consent.  However, public international law doctrine provides important rules to ensure greater harmony and accountability for interstate relations.

State and Non-State Relations

Public international law also regulates obligations between states and non state entities such as international organizations (groups whose members are sovereign states, including the United Nations and the European Union), as well as affiliated nongovernmental organizations (such as the International Monetary Fund and the World Bank), and in some cases private entities like corporations (through public concession agreements and regulations on world trade).  In fact, international organizations are playing an increasingly important role as independent actors in international relations, as evidenced by the influence IMF loan conditions may have on a developing nation’s economy, or the weight of a U N Resolution authorizing the use of force.  International organizations have independent international legal personalities and may enter into agreements with each other or with states that are bound by similar rules as those that apply to treaties between states. 


Individual Rights under International Law

As a rule, international law places obligations and duties upon states and international organizations rather than individuals.  Increasingly, however, international law has directly addressed individual rights and provided remedies for individuals to challenge the actions of international entities.  Most individual rights are set forth in the body of human rights law that is defined by five treaties and protocols commonly referred to as the International Bill of Human Rights. These agreements are:  1) Universal Declaration of Human Rights; 2) International Covenant on Economic, Social and Cultural Rights; 3) International Covenant on Civil and Political Rights; 4) Optional Protocol to the International Covenant on Civil and Political Rights; and 5) Second Optional Protocol to the International Covenant on Civil and Political Rights. Together they establish that all individuals have basic rights to life, freedom of religion, movement, association and ideas, as well as rights to non-discriminatory treatment and fair judicial processes.  Additional human rights instruments guarantee special rights for women and children as well as vulnerable groups like ethnic and racial minorities and refugees.  Although international human rights law does not give rise to individual remedies per se (in that enforcement remains the duty of the signatory state), official monitoring bodies and private nongovernmental organizations, have been established to press states to observe fundamental human rights set forth in the treaties and to intervene as possible on individuals’ behalf. 



Dispute Resolution: Unlike a domestic justice system, there is no universally recognized arbiter of public international law.  International law does, however, set some basic rules for addressing international disputes.  The Vienna Convention on Treaties, for example, sets out the basic rules for interpreting and enforcing treaties among states.  The Vienna Conventions on Diplomatic Relations and on Consular Relations establish the basic legal principles for the conduct of diplomacy.  The UN Charter provides a framework for addressing threats to international peace (through the Rules and Procedures of the Security Council) as well as a variety of economic and social problems (through the agencies that are subsets of the General Assembly).  The International Court of Justice, the judicial arm of the United Nations, provides a forum with limited jurisdiction for states to resolve disputes between each other that arise under international law.  Likewise, the International Criminal Court applies a set of procedures applicable to all member states to hear cases of individual criminal responsibility that arise under international criminal law.  Ultimately, however, the enforceability of public international law in a given state or entity depends largely on that state’s willingness to apply it.

Domestic Enforcement: Most countries, including the United States, recognize and apply international law with the same weight as national law, provided that the international law is properly adopted and recognized.  In the case of treaties and conventions, states must have ratified the agreement in accordance with their national laws for it to apply domestically.  In this regard, states fall into two camps.  The unitary model followed by many civil law countries holds that when a treaty or convention is signed by the head of state, it becomes binding on the signing country on its own terms.  The dualist model holds that while a head of state may bind the country to abide to a treaty’s terms by signing it, separate legislation must be passed by the national legislature in order to give the terms domestic legal effect.  The United States falls into the latter category, as the Constitution requires that all treaties and conventions be ratified by a two-thirds majority of the Senate.


Contemporary Issues

International law is constantly evolving according to the creation of new conventions, treaties and state decisions that respond to ever-shifting current events.  In the last few decades, however, there has been a clear trend toward the increased importance and applicability of public international law to states’ foreign policies as well as to the protection of individual rights.   This trend can be seen in two contemporary examples that are at the forefront of the debate over public international law.  One is the increased recognition of international humanitarian law (IHL) as it applies to state interventions in internal conflicts, such as military operations in Lebanon, Iraq and Afghanistan.  The second is the field of international criminal law (ICL), which assigns individual criminal responsibility for international crimes, has grown significantly in recent years with the advent of the International Criminal Tribunals for the former Yugoslavia, Rwanda, and Sierra Leone and by the creation of the International Criminal Court.  By these mechanisms, international law is becoming increasingly prominent as a factor in governing actions within states rather than restricting itself to interactions among them.

International Humanitarian Law

International humanitarian law (IHL) is the subset of public international law that governs the conduct of hostilities between states and aims to protect civilians and other noncombatants from abuse or harm.  It includes the Four Geneva Conventions (often referred to as “the Laws of War”), the United Nations Charter and the Convention on the Prevention and Punishment of Genocide.  These conventions each impose on states the obligation to behave in accordance with certain minimum standards and agreed universal norms in the treatment of soldiers and civilians in conflict.

While most IHL doctrine deals with conflicts between recognized states, Common Article 3 to the Geneva Conventions and its Additional Protocol II of 1977 directly address the need to treat civilians and other noncombatants humanely in cases of non-international conflict.  (See Hamdan v. Rumsfeld, 548 U. S. (2006)).  Common Article 3 provides that in any armed conflict, whether it occurs between government forces and one or more non state armed groups, or between armed groups fighting among themselves, no party may kill noncombatants, take them hostage or subject them to “outrages upon personal dignity, in particular humiliating and degrading treatment... or the passing of sentences and the carrying out of executions without previous judgment pronounced by a regularly constituted court, affording all the judicial guarantees which are recognized as indispensable by civilized peoples.” 

International Criminal Law

The separate field of international criminal law (ICL) offers a distinct departure from the principle of state responsibility;  under ICL, victims may themselves assert claims in appropriate forums against individuals in other states that have violated international law.  ICL essentially began as part of the statutes of the war crimes tribunals established in Nuremberg and Tokyo to try individuals responsible for atrocities committed during the Second World War.  More recently, the International Tribunals for the former Yugoslavia and for Rwanda were established by the United Nations to prosecute individuals responsible for the most serious international crimes committed during the conflicts in those countries.  And most recently, the International Criminal Court assumed jurisdiction for adjudicating complaints against individuals responsible for the most serious forms of war crimes.

All of these tribunals apply international criminal law that includes Grave Breaches of the Geneva Conventions, Genocide, Aggression and Crimes against Humanity.  But unlike other subjects of international law, these crimes concern the rights and accountability of individuals rather than the state.  Most grave offences in international criminal law are recognized universally and depending on a court’s jurisdictional statute, can be prosecuted anywhere according to the same substantive and procedural norms.  In fact, several states (most notably Belgium and Spain) have now recognized universal jurisdiction for violations of international criminal law that enable prosecutions of perpetrators who otherwise have no connection to the state in which they are tried.


Text provided by Scott Worden and Professor Paul Williams, Faculty of Law, American University