How sovereign states communicate, make binding commitments, resolve disputes, and build frameworks for cooperation in a world without a central governing authority
Every year, diplomats from dozens of countries gather in ordinary-looking conference rooms — in Geneva, Vienna, New York, Brussels, and countless other cities — and attempt to do something genuinely remarkable: convince sovereign governments to behave in ways those governments would not necessarily choose on their own. They negotiate. They write documents. They make promises. They exchange ambassadors, sign agreements, and establish courts. And through this slow, painstaking process of dialogue and commitment, they build the scaffolding of international order.
Diplomacy is one of the oldest institutions in human civilization. Ancient city-states sent envoys to neighboring powers to arrange peace, trade, and marriage alliances. The Greek city-states maintained a tradition of diplomatic immunity so that messengers could travel safely even between warring parties. Medieval European monarchs exchanged embassies and negotiated concordats with the papacy. The modern system of professional diplomacy — with resident ambassadors, foreign ministries, formal protocols, and multilateral conferences — emerged gradually over several centuries, taking shape most clearly after the Peace of Westphalia in 1648 and accelerating through the nineteenth and twentieth centuries.
What makes diplomacy distinctive as a political institution is that it must function in an environment where there is no central authority. Within a country, disputes are resolved by courts, laws are enforced by police, and authority flows through recognized governmental institutions. Between countries, no such central authority exists. States are sovereign. No government sits above them to enforce agreements, punish violations, or compel compliance. And yet, diplomacy and international law work — imperfectly, inconsistently, but genuinely — because states find it in their interest to cooperate, because reputation matters, because institutions create expectations, and because political leaders and citizens increasingly understand that many of the world's most pressing problems cannot be solved by any single country acting alone.
This chapter examines how diplomacy, treaties, and international law function in the real world of international relations. It begins with the basic question of what diplomacy does — not just the ceremonial image of white-gloved ambassadors at formal dinners, but the day-to-day work of representing governments, negotiating agreements, gathering information, managing crises, and maintaining the channels of communication that make cooperation possible. It then examines treaties and international agreements as the primary legal instruments through which states make binding commitments to one another. It explores how recognition and sovereignty shape diplomatic relations. It explains the nature and scope of international law — what kind of law it is, where it comes from, how it is applied, and why it is so difficult to enforce. It looks at the use of sanctions as a tool of diplomatic pressure. It examines international courts and arbitration as mechanisms for resolving disputes. And it concludes by confronting one of the central puzzles of international relations: why states sometimes follow international law even when no one can force them to.
Understanding these institutions matters not only for students of political science or international relations. It matters for citizens in every country, because the agreements their governments make — on trade, on climate, on arms control, on human rights, on health — shape the conditions of their daily lives in ways that domestic politics alone cannot address. It matters for understanding the news: why countries break diplomatic relations, what sanctions actually accomplish, how international criminal tribunals work, and why some international agreements hold while others collapse. And it matters because the international system, for all its messiness and imperfection, is one of the great achievements of political life — an ongoing, often frustrating, but genuinely important attempt to create order among sovereign equals.
A foreign government has been credibly accused of using chemical weapons against civilians within its own borders. The evidence is compelling, but the government denies the charges. The United Nations Security Council cannot act because one permanent member threatens to veto any enforcement resolution. Several states want to impose economic sanctions; others fear humanitarian consequences for the civilian population. By the end of this chapter, you will have the conceptual tools to analyze this situation — understanding what international law says, what diplomatic mechanisms exist, what constraints apply, and why the international community often struggles to enforce norms it has formally adopted.
The following terms will be defined and explained in this chapter. Pay attention to each as it appears.
Diplomacy is the conduct of relations between sovereign states and other international actors through peaceful communication, representation, and negotiation. It is the primary means by which governments interact with one another, express their interests, manage conflicts, build agreements, and coordinate responses to shared problems. Diplomacy is not synonymous with foreign policy — foreign policy refers to the goals and strategies a government pursues in international relations, while diplomacy is the set of institutions, processes, and practices through which foreign policy is actually conducted.
The word "diplomacy" derives from the Greek word diploma, meaning a folded document, because official communications between rulers were written on documents folded and sealed in a distinctive way. The term came to refer to the credentials carried by envoys, and eventually to the entire practice of official interstate communication. Today the word carries several related meanings: the professional conduct of international relations, the skill of managing negotiations effectively, and the broader culture and etiquette of interstate dealings.
The most basic function of diplomacy is representation. A state's diplomats act as the official voice and presence of their government in a foreign country. Through their ambassador and embassy staff, a government communicates its positions, concerns, interests, and requests to the host government. This representation function operates continuously, not only during moments of crisis or negotiation. Diplomats attend government ceremonies, make official statements, relay messages between capitals, and maintain the ongoing channels of communication through which states conduct their relationships.
Representation also involves protecting the interests of a state's own citizens abroad. When a citizen of one country is arrested, detained, injured, or killed in another country, the embassy of the citizen's home country typically becomes involved — providing consular assistance, monitoring legal proceedings, and advocating on the citizen's behalf within the limits of the host country's legal system. This consular function is one of the most practically important roles that diplomatic missions perform.
Diplomats negotiate. They are the primary agents through which governments work out the terms of agreements — commercial treaties, defense alliances, arms control agreements, environmental commitments, trade arrangements, border demarcations, prisoner exchanges, ceasefire terms, and countless other arrangements. Negotiation is not simply a matter of asking for what you want and compromising until agreement is reached. It involves deep knowledge of the other party's interests and constraints, careful management of domestic political pressures, creative construction of deals that serve multiple parties' needs, and the patient building of trust over time.
Modern diplomatic negotiations often involve large teams — legal experts, technical specialists, economists, military advisors, communications officers — working alongside professional diplomats. Negotiations for major multilateral agreements, such as climate accords or trade frameworks, can take years and involve hundreds of officials from dozens of countries.
An often-underappreciated function of diplomacy is information gathering and analysis. Diplomats are the eyes and ears of their governments abroad. They observe political developments in the host country, assess the stability and direction of foreign governments, report on public opinion, analyze economic conditions, and provide their home governments with the information needed to make foreign policy decisions. This informational function was especially critical in earlier centuries when communication was slow and expensive; it remains important today because no government can understand world affairs through news media alone.
Diplomatic reports — called cables or diplomatic dispatches — have historically been among the most valuable sources of political intelligence available to governments. The 2010 disclosure of hundreds of thousands of U.S. diplomatic cables through WikiLeaks offered the public an unusually candid view of what diplomats actually report and how bluntly they assess foreign governments, allies, and rivals.
One of diplomacy's most important functions is preventing disputes from escalating into violent conflicts. When tensions rise between states — over border incidents, trade disputes, espionage accusations, minority rights violations, territorial claims, or any number of other flashpoints — diplomats are often the first responders. They communicate positions and intentions to reduce the risk of miscalculation, establish channels for ongoing dialogue, propose de-escalatory measures, and work to find face-saving formulas that allow both sides to step back from confrontation without appearing to capitulate.
Crisis diplomacy — the intense, high-pressure diplomatic activity during acute international crises — is among the most demanding work in the profession. During the Cuban Missile Crisis of 1962, back-channel communications between U.S. and Soviet officials helped prevent a nuclear confrontation that the formal military postures of both sides seemed to be heading toward. During diplomatic crises, the difference between a well-managed communication and a misread signal can be enormously consequential.
Modern diplomacy has increasingly moved beyond bilateral interactions between two states to multilateral settings involving many states simultaneously. Multilateral diplomacy — conducted in international organizations, treaty conferences, multilateral forums, and summit meetings — has become central to how the international system functions. The United Nations General Assembly, the Conference of Parties to climate agreements, World Trade Organization dispute panels, G7 and G20 summits, and countless other forums bring together representatives of many states to address shared problems, negotiate frameworks, and coordinate responses.
Multilateral diplomacy is more complex than bilateral diplomacy in several respects. Coalition-building becomes critical: states seek allies to strengthen their negotiating positions. Procedural rules matter enormously, because the rules governing voting, agenda-setting, and committee structure can determine outcomes as much as substantive arguments. And the need to satisfy many parties simultaneously — each with different interests and domestic political constraints — makes reaching and sustaining agreement far more difficult.
The institutions through which diplomacy is conducted have evolved over centuries into a recognizable global system. Understanding how these institutions work helps students appreciate what diplomacy is in practice, as opposed to its popular image.
At the center of each state's diplomatic system is its foreign ministry — known in the United States as the Department of State, in the United Kingdom as the Foreign, Commonwealth and Development Office, in France as the Ministère de l'Europe et des Affaires étrangères, and by various other names in other countries. The foreign ministry is the central government department responsible for conducting foreign relations. It houses the professional diplomatic corps, coordinates policy across government departments, maintains diplomatic archives, issues passports and travel documents, and manages the network of embassies, consulates, and missions abroad.
The head of the foreign ministry — the Secretary of State in the United States, the Foreign Secretary in the United Kingdom, the Foreign Minister in most other countries — is typically a senior member of the cabinet, often among the most powerful ministers in a government. In some systems, however, real foreign policy authority rests primarily with the head of state or government, with the foreign minister playing a more implementing and coordinating role.
Professional foreign ministry staff — foreign service officers or career diplomats — spend their careers moving between assignments in their country's capital and postings abroad. They develop expertise in particular regions, languages, and issue areas. This professional corps provides continuity and institutional memory across changes of government, though in some countries, particularly the United States, many senior diplomatic appointments go to political figures rather than career diplomats.
An embassy is the official diplomatic mission of one state within another state. It serves as the seat of the ambassador and the full diplomatic staff, and it performs the full range of diplomatic functions: representation, negotiation, reporting, consular services, and crisis management. The embassy building itself, and the grounds it sits on, enjoy a special legal status under international law: they are inviolable, meaning that agents of the host government may not enter without permission.
The ambassador is the highest-ranking diplomatic representative of one state to another. Ambassadors are formally accredited to the head of state of the receiving country and present their credentials — a formal letter of introduction from their head of state — at an official ceremony upon arrival. Below the ambassador, embassy staff include political officers, economic officers, consular officers, military attachés, public affairs officers, and administrative staff. Major embassies in important countries can have dozens or even hundreds of staff; small embassies in less significant bilateral relationships may have only a handful.
Consulates are diplomatic offices that handle primarily consular functions. While embassies are typically located in a country's capital and handle the full spectrum of diplomatic relations, consulates are often located in major commercial cities or border areas and focus on issuing visas, assisting citizens of their country abroad, certifying documents, and promoting trade. Consular officers enjoy more limited legal protection than diplomats accredited to the embassy, and consulates are not full diplomatic missions in the same sense as embassies.
One of the most important and sometimes controversial features of the diplomatic system is diplomatic immunity — the legal protection from prosecution and most civil proceedings that host states must extend to accredited diplomats. Under the Vienna Convention on Diplomatic Relations (1961), diplomats enjoy near-absolute immunity from the criminal jurisdiction of the receiving state and broad immunity from civil jurisdiction. This immunity extends to diplomats' family members living with them.
The rationale for diplomatic immunity is functional: without it, states could harass, arrest, or prosecute foreign diplomats to gain leverage, retaliate for policy disagreements, or silence inconvenient communications. Immunity ensures that the channels of diplomatic communication remain open even when relations are strained. The problem with diplomatic immunity is that it can shield serious wrongdoing. Diplomats have claimed immunity to avoid prosecution for crimes ranging from traffic violations to serious offenses. When a diplomat commits a crime, the receiving state's typical remedy is to declare the diplomat persona non grata — an unwelcome person — requiring the sending state to recall them.
Persona non grata is a Latin phrase meaning "unwelcome person." In diplomatic practice, it refers to the formal declaration by a host government that a specific diplomat must leave the country. A government can declare any diplomat persona non grata at any time, without providing reasons. The sending state must then recall the diplomat or risk having that person lose their diplomatic status and legal protections. Declarations of persona non grata are a common diplomatic tool for expressing displeasure or removing a diplomat suspected of espionage. Expelling diplomats is a frequent response to espionage discoveries; the expelled diplomat's government often responds by expelling one of the other country's diplomats in turn — a practice sometimes called tit-for-tat expulsion.
International diplomatic negotiations typically follow a structured process, though the details vary widely depending on the subject matter, the number of parties, and the political context.
A treaty is a formal, binding agreement between two or more sovereign states, governed by international law. Treaties are the most important legal instruments in international relations — the primary means through which states create enforceable mutual obligations. The word "treaty" is sometimes used broadly to refer to any international agreement, and sometimes more narrowly to refer to formal agreements requiring legislative ratification, in contrast to executive agreements or other less formal arrangements.
The foundational principle governing treaties is pacta sunt servanda — Latin for "agreements must be kept." This principle, recognized in customary international law and codified in the 1969 Vienna Convention on the Law of Treaties, holds that states are bound by treaty commitments they have freely undertaken and must perform them in good faith. Pacta sunt servanda is one of the most basic norms of international legal order; without it, treaties would be worthless.
The Vienna Convention on the Law of Treaties is itself a treaty — an agreement among states setting out the rules governing how treaties are made, interpreted, amended, and terminated. It provides definitions, procedural rules, and legal standards that have shaped international treaty practice significantly since its entry into force in 1980.
International agreements come in many forms, and the terminology is not always used consistently. Bilateral treaties are agreements between two states, covering an enormous range of subjects: trade and commerce, extradition of criminal suspects, defense alliances, tax matters, investment protection, cultural exchange, environmental protection, and more. Multilateral treaties involve three or more states, sometimes dozens or hundreds. Major multilateral treaties — such as the United Nations Charter, the Geneva Conventions, the Nuclear Non-Proliferation Treaty, and the Paris Agreement on climate change — involve nearly all the world's states and establish major frameworks for international order.
Protocols are supplementary agreements that add to or modify an existing treaty. The Kyoto Protocol, for example, was a protocol to the United Nations Framework Convention on Climate Change, adding specific emissions reduction commitments. Executive agreements are international agreements concluded by the executive branch without the legislative ratification required for formal treaties. In the United States, presidents have increasingly used executive agreements rather than formal treaties — in part because treaties require Senate approval by a two-thirds majority, a threshold that is very difficult to achieve for controversial agreements. Executive agreements are legally valid under U.S. law and binding on the United States internationally, but they can be more easily reversed by a successor president. Memoranda of Understanding (MOUs) and other less formal arrangements often do not carry formal legal binding force under international law but establish political commitments and shared understandings between governments.
A treaty enters into force — becomes legally binding — according to the terms specified in the treaty itself. Most multilateral treaties specify a number of ratifications required before the treaty takes effect; the Rome Statute of the International Criminal Court required 60 ratifications. Bilateral treaties typically enter into force after both parties have exchanged instruments of ratification.
When signing or ratifying a multilateral treaty, states often attach reservations — declarations that they will not be bound by certain provisions or that they interpret certain provisions in a particular way. Reservations allow states to join broad international agreements while carving out specific obligations they find unacceptable. The Vienna Convention on the Law of Treaties governs when reservations are permissible: a reservation cannot be contrary to the object and purpose of the treaty as a whole.
States can withdraw from treaties, though the conditions depend on the treaty's terms and circumstances. Most modern treaties contain explicit withdrawal provisions requiring a certain period of notice. The United States' withdrawal from the Paris Agreement on climate change under the Trump administration (2017), and subsequent re-accession under the Biden administration (2021), illustrated how quickly a country can exit and re-enter treaty frameworks depending on changes in political leadership. Some withdrawals are more legally contested. The doctrine of rebus sic stantibus — a qualification to pacta sunt servanda — holds that treaties may be terminated when the circumstances that existed at the time of conclusion have fundamentally changed. But this doctrine is interpreted narrowly and cannot simply be invoked whenever a state finds a treaty burdensome.
Pacta sunt servanda is a Latin phrase meaning "agreements must be kept." It is one of the oldest and most fundamental principles of international law, holding that states are legally and morally bound to fulfill the commitments they have voluntarily undertaken in treaties. Without this principle, treaties would serve no purpose; states would have no reason to trust each other's commitments or to invest effort in negotiations. Pacta sunt servanda does not mean that treaty obligations are absolute under all circumstances — international law recognizes grounds for suspension or termination in certain extraordinary situations. But it establishes a strong presumption of binding force that can only be overcome in limited circumstances. The principle is also foundational to domestic contract law in most legal systems, reflecting the broader importance of promise-keeping as a foundation of cooperative social life.
One of the most politically charged aspects of diplomatic practice is the question of recognition — whether one state officially acknowledges the legal existence and legitimate government of another. Recognition may seem like a mere formality, but it carries significant legal and political consequences.
Under international law, a state is generally considered to exist as a legal entity when it meets certain factual criteria: a defined territory, a permanent population, an effective government, and the capacity to enter into relations with other states. These criteria, derived from the 1933 Montevideo Convention on the Rights and Duties of States, describe what states are. But recognition by other states matters enormously for practical purposes: an unrecognized state cannot enter into treaties, cannot join international organizations, cannot access international financial institutions, and cannot enjoy full participation in the international community.
De jure recognition is formal legal recognition that a state or government exists and is legitimate. When one state extends de jure recognition to another, it acknowledges that the recognized entity is a legitimate state with full legal standing in international relations. De facto recognition is a more limited acknowledgment that an entity exercises effective control over territory and population, without necessarily affirming its legitimacy. States sometimes extend de facto recognition to governments or entities they deal with for practical purposes but whose legitimacy they contest.
Recognition decisions are deeply political. States extend or withhold recognition to signal approval or disapproval, to advance their strategic interests, or to reward and punish. The United States' recognition of the People's Republic of China in 1979 — shifting recognition from the Republic of China (Taiwan) — was a major diplomatic realignment driven by strategic calculations about countering Soviet power. Many countries have not recognized Kosovo, which declared independence from Serbia in 2008, because doing so would set a precedent for separatist movements within their own borders. Most legal scholars hold that a state, once widely recognized, retains legal personality even if some states withdraw recognition or break diplomatic relations.
States can sever diplomatic relations — withdraw their ambassadors and close their embassies — without withdrawing recognition of the other state's legal existence. Breaking diplomatic relations is a serious diplomatic step, signaling profound displeasure or incompatibility, but it is distinct from non-recognition. The United States and Cuba maintained no diplomatic relations from 1961 to 2015, during which they had to deal with each other on various matters through third-party intermediaries. When states wish to maintain some channel of communication despite broken diplomatic relations, they sometimes use third-party states or neutral missions to convey messages. Switzerland has historically served as a "protecting power" representing one state's interests in another country with which it has no diplomatic relations.
The tension between two competing principles of international law — the right of peoples to self-determination and the principle of territorial integrity — has made the recognition of new states one of the most contested areas of international relations.
When Yugoslavia dissolved in the early 1990s, European Community states were initially cautious about recognizing the successor republics, fearing it would encourage separatism. Germany, however, pushed for early recognition of Slovenia and Croatia — a decision others criticized as precipitating violence but that Germany defended as supporting self-determination. The international community eventually recognized Bosnia, Croatia, Slovenia, and later other successor states, but the process was chaotic and contested.
Kosovo's 2008 declaration of independence from Serbia provoked a divided response. The United States, most EU members, and many other states extended recognition. Russia, China, and Serbia did not. The International Court of Justice, asked to rule on whether Kosovo's declaration violated international law, issued an advisory opinion in 2010 holding that the declaration itself did not violate international law — but this addressed only the legality of the declaration, not whether Kosovo had a right to statehood under international law.
Palestine presents an ongoing case of partial recognition: as of 2024, over 140 of the United Nations' 193 member states recognize Palestine as a state, but major Western powers including the United States have not. These cases illustrate that recognition is not simply a legal determination based on objective criteria, but a political act reflecting the interests, values, and relationships of the recognizing state.
International law is the body of rules, principles, and norms that governs relations between states and other international actors. It is one of the most fascinating and contested areas of legal study, in part because it operates without a central legislature to create it, a universal executive to enforce it, or a compulsory court system to adjudicate it — and yet it exists, it functions, and it shapes the behavior of states in significant ways.
Where does international law come from? The Statute of the International Court of Justice, in Article 38, provides the canonical answer by listing the sources the Court is to apply. Treaties and conventions are the most visible source. When states negotiate and ratify treaties, they create binding legal obligations for themselves. The law created by a treaty is binding on its parties but does not automatically bind states that have not ratified it.
Customary international law arises from the consistent practice of states accompanied by a sense of legal obligation. When states behave in a particular way over time and do so because they believe they are legally required to — not merely because it is convenient — that practice can crystallize into customary international law binding on all states, including those that have not signed any treaty on the subject. Establishing customary international law requires two elements: state practice (what states actually do) and opinio juris (the belief that the practice is legally required). Identifying customary international law involves examining diplomatic documents, national legislation, court decisions, military manuals, and other evidence of what states do and why.
General principles of law recognized by civilized nations — a third source recognized in Article 38 — refers to principles common to the domestic legal systems of most states, such as good faith, the prohibition of unjust enrichment, and basic procedural fairness. These principles can fill gaps in international law where neither treaties nor custom provide clear answers. Judicial decisions and scholarly writings are recognized as subsidiary means for determining rules of international law.
A special category of international legal rules consists of jus cogens norms — peremptory norms from which no derogation is permitted. Unlike ordinary rules of international law, which states can modify among themselves through treaties, jus cogens norms are so fundamental that no agreement between states can authorize or justify their violation. The Vienna Convention on the Law of Treaties declares that any treaty conflicting with a jus cogens norm is void. Examples of recognized jus cogens norms include the prohibition of genocide, the prohibition of slavery and slave trade, the prohibition of torture, the prohibition of crimes against humanity, and the prohibition of aggression. These represent the absolute floor of international legal obligation.
Critics have long questioned whether international law is "really" law in any meaningful sense. The legal philosopher John Austin defined law as commands from a sovereign backed by sanctions. By this definition, international law fails the test: there is no sovereign above states, and sanctions for violation are inconsistent and often absent.
Most international legal scholars reject Austin's positivist definition as too narrow and argue that international law is genuine law for several reasons. First, states themselves treat international law as genuinely binding — they cite it in legal proceedings, build it into domestic legislation, and argue about its content in ways that would be pointless if it were merely aspirational. Second, compliance with international law is actually quite high for most rules in most circumstances — states follow international norms far more often than they violate them. Third, violations of international law produce real consequences — reputational damage, diplomatic protests, exclusion from international bodies, economic sanctions, and sometimes military responses. The more useful question is not whether international law is "really" law, but how it operates differently from domestic law and why its compliance record varies so dramatically across different subject areas.
Customary international law consists of rules that have emerged from the consistent and general practice of states, followed out of a sense of legal obligation rather than mere habit or convenience. Unlike treaty law, which binds only parties that have expressly agreed to it, customary international law is generally binding on all states — including those that have never signed a treaty on the subject. The prohibition of piracy on the high seas, the rule that foreign sovereign states cannot be sued in domestic courts without their consent, and the basic rules of diplomatic immunity all developed initially as customary international law before being codified in treaties. Customary international law continues to develop as state practice evolves, though identifying precisely when a practice has crystallized into a binding legal norm requires careful analysis of what states actually do and why they do it.
When international law or diplomatic norms are violated, states have limited but real tools for expressing displeasure and applying pressure. The most common such tool is the sanction — a deliberate restriction of normal relations imposed to signal condemnation and create incentives for changed behavior.
Economic sanctions restrict trade, investment, or financial relations. They may ban imports or exports of certain goods, prohibit financial transactions, freeze assets, or exclude the target from international banking systems. Economic sanctions vary enormously in their scope and intensity, from narrow targeted restrictions to comprehensive embargoes. Financial sanctions specifically target financial flows — blocking access to international banking systems, particularly the U.S. dollar-denominated financial system, given the dollar's central role in international finance. Targeted sanctions (sometimes called "smart sanctions") focus on specific individuals — government officials, business figures, military commanders — rather than on an entire economy. They may include asset freezes, travel bans, and exclusion from the international financial system, attempting to impose costs on decision-makers without causing broader humanitarian harm on civilian populations.
Diplomatic sanctions involve the downgrading or severing of diplomatic relations — withdrawing ambassadors, closing embassies, canceling state visits, or expelling diplomats. Multilateral sanctions imposed by many states acting collectively — either through the United Nations Security Council under Chapter VII of the UN Charter, which can impose legally binding sanctions on member states, or through coordinated action by groups of states such as the European Union or G7 — are generally more effective than unilateral measures.
The effectiveness of sanctions is one of the most debated questions in foreign policy. The evidence is genuinely mixed. Sanctions have contributed to policy changes in some cases — international sanctions on apartheid South Africa, combined with other forms of pressure, played a role in the transition to democracy, though scholars debate how decisive they were. Comprehensive sanctions on Iraq in the 1990s imposed enormous humanitarian costs on the Iraqi population without removing Saddam Hussein from power. Sanctions against Iran over its nuclear program, followed by the negotiation of the 2015 Joint Comprehensive Plan of Action, represent a case where sustained multilateral sanctions appear to have helped bring Iran to the negotiating table, though Iran's nuclear program has continued to develop.
Research suggests that sanctions are more likely to be effective when they are multilateral rather than unilateral (making evasion harder); the targeted country is economically dependent on the sanctioning states; the goals are limited and specific rather than demanding regime change; the target country has some democratic accountability; and they are combined with credible promises of sanctions relief if behavior changes. Sanctions often fail to change behavior because target states can adapt, find alternative trading partners, or mobilize nationalist sentiment to resist external pressure.
The United States imposes more unilateral sanctions than any other country. U.S. sanctions derive much of their power from the centrality of the dollar in international finance: because so much of global trade and finance flows through dollar-denominated systems and U.S.-regulated financial institutions, U.S. financial sanctions can affect foreign entities that are not themselves American. This "extraterritorial" reach of U.S. sanctions has been a source of persistent friction with U.S. allies. Multilateral sanctions imposed by the UN Security Council are legally binding on all member states under Chapter VII of the UN Charter. But because any of the five permanent members can veto Security Council action, such sanctions can only be imposed when the major powers agree.
States in dispute with each other — or in dispute over treaty obligations — have access to a growing array of international courts and arbitration bodies for peaceful resolution of their differences. These institutions represent one of the most significant developments in international law over the past century.
The International Court of Justice (ICJ) is the primary judicial organ of the United Nations, established in 1945 under the UN Charter. Located at The Hague in the Netherlands, the ICJ settles legal disputes between states and gives advisory opinions on legal questions referred to it by UN organs and specialized agencies. The ICJ consists of 15 judges elected by the UN General Assembly and Security Council for nine-year terms.
The ICJ's jurisdiction over contentious cases — actual disputes between states — depends on state consent. The Court cannot simply take up a case; the states involved must have consented to its jurisdiction, either through a special agreement to submit a particular dispute, through a provision in a treaty that subjects disputes to ICJ jurisdiction, or through the "optional clause" mechanism by which states accept compulsory ICJ jurisdiction over future disputes with other states that have also accepted it. The United States withdrew its acceptance of compulsory ICJ jurisdiction in 1986 after the Court ruled against it in a case brought by Nicaragua.
When states have consented to ICJ jurisdiction and a judgment is rendered, they are legally bound to comply. However, enforcement is problematic: the UN Security Council can take action to ensure compliance with ICJ judgments, but any of the five permanent members can block such action. The ICJ's advisory opinion function — rendering opinions on legal questions without binding force — has contributed significantly to international legal understanding. Advisory opinions on the legality of nuclear weapons (1996), on the construction of a wall in occupied Palestinian territory (2004), and on Kosovo's independence (2010) have clarified important legal questions, though they bind no one.
The International Criminal Court (ICC), established by the Rome Statute and operational since 2002, is a fundamentally different institution from the ICJ. While the ICJ adjudicates disputes between states, the ICC prosecutes individuals for international crimes: genocide, crimes against humanity, war crimes, and the crime of aggression. The ICC represents the institutionalization of the principle that individuals — including heads of state and government — can be held personally accountable under international law for the most serious crimes.
The ICC can exercise jurisdiction over crimes committed on the territory of states parties to the Rome Statute, over crimes committed by nationals of states parties, and over situations referred to the Court by the UN Security Council. The principle of complementarity governs the ICC's relationship with national courts: the ICC is intended to act only when national justice systems are unwilling or unable to genuinely prosecute serious crimes. The Court is not meant to replace domestic criminal justice but to complement it as a last resort.
The ICC has been significant but also deeply contested. Critics include the United States, Russia, China, and India, none of which are parties to the Rome Statute; African states and organizations that have accused the Court of disproportionate focus on African leaders; and scholars who argue that the Court's prosecutorial decisions have interfered with peace negotiations. The ICC's indictment of Vladimir Putin in 2023 for the alleged deportation of Ukrainian children was a landmark — the first indictment of a sitting major-power leader — though its enforcement depended entirely on the willingness of states to arrest and transfer him, which none appeared inclined to do.
Arbitration is a form of dispute resolution in which parties agree to submit their dispute to a tribunal of arbitrators whose decision they commit in advance to accept as binding. International arbitration is widely used in commercial disputes between private parties and between states and foreign investors, and it is increasingly used to resolve disputes between states on issues ranging from maritime boundaries to investment treaty violations. The Permanent Court of Arbitration (PCA), despite its name, is not a standing court but an intergovernmental organization that facilitates arbitration. The International Centre for Settlement of Investment Disputes (ICSID) handles arbitration between states and foreign investors under bilateral investment treaties.
The 2016 arbitration award in the South China Sea case — in which the Philippines brought claims against China's maritime claims under the United Nations Convention on the Law of the Sea — illustrated both the potential and limitations of international arbitration. The tribunal issued a comprehensive ruling largely favorable to the Philippines. China, however, rejected the tribunal's jurisdiction and refused to comply with the award. The Philippines subsequently softened its posture toward China for diplomatic and economic reasons, leaving the award largely unenforced.
Beyond the ICJ and ICC, many specialized international and regional courts have developed. The European Court of Human Rights (ECHR) adjudicates cases brought by individuals against Council of Europe member states for violations of the European Convention on Human Rights; it has issued thousands of judgments, many of which member states have complied with, leading to legislative changes and domestic legal reforms. The International Tribunal for the Law of the Sea (ITLOS) adjudicates disputes arising under the United Nations Convention on the Law of the Sea. The World Trade Organization's Dispute Settlement Body adjudicates trade disputes between WTO member states and is among the most heavily used international dispute settlement mechanisms. Various regional courts — the Court of Justice of the European Union, the Inter-American Court of Human Rights, the African Court on Human and Peoples' Rights — exercise jurisdiction within their respective regions.
| Court or Body | Who It Adjudicates | Jurisdiction Basis | Key Limitation |
|---|---|---|---|
| International Court of Justice (ICJ) | Disputes between states; advisory opinions for UN bodies | State consent (optional clause or special agreement) | No compulsory jurisdiction; enforcement relies on Security Council |
| International Criminal Court (ICC) | Individuals for genocide, crimes against humanity, war crimes, aggression | Territory of states parties, nationals of states parties, Security Council referrals | Major powers (U.S., Russia, China) are not parties; depends on state cooperation for arrests |
| Permanent Court of Arbitration (PCA) | States, state entities, intergovernmental organizations, private parties | Arbitration agreement between parties | Parties must agree to submit; compliance depends on voluntary acceptance |
| European Court of Human Rights (ECHR) | Individuals against Council of Europe member states | Membership in the Council of Europe and European Convention on Human Rights | Limited to Europe; compliance has declined in some member states |
| WTO Dispute Settlement Body | Trade disputes between WTO member states | WTO membership and acceptance of dispute settlement procedures | Appellate Body has been hamstrung by U.S. blocking of new judge appointments |
The International Court of Justice in The Hague handles a relatively small caseload compared to domestic courts — typically a few dozen active cases at any time — but its cases often involve questions of fundamental importance to international order. A typical ICJ case might concern a maritime boundary dispute between neighboring states, the interpretation of a bilateral treaty, allegations of violations of international law during an armed conflict, or claims regarding the treatment of a state's nationals abroad.
The ICJ's procedures are formal and deliberate. Written submissions — called memorials and counter-memorials — are exchanged over a period of months or years, often running to thousands of pages. Oral hearings before the full court follow. Deliberation by the judges produces a majority judgment, often accompanied by concurring and dissenting opinions. The entire process from filing to judgment typically takes several years for complex cases.
A notable recent example: the case that South Africa brought against Israel in January 2024 under the Genocide Convention, alleging that Israel's military operations in Gaza constituted or risked genocide. The ICJ issued provisional measures — orders to Israel to take all measures to prevent acts that could fall under the Genocide Convention — while declining to order a ceasefire. The case illustrated how the ICJ can generate significant political attention and legal discussion even when its enforcement mechanisms remain limited. The ICJ's judgments are legally binding on the parties to a case. Compliance is generally good — most states, most of the time, comply with ICJ judgments, in part because of reputational concerns and in part because losing states often find compliance more manageable than the political costs of defiance.
The enforcement problem in international law is both real and sometimes overstated. Understanding it requires moving beyond the simple observation that there is no world police force to more nuanced analysis of why states comply or defect, and what factors affect the reliability of international legal obligations.
The fundamental structural feature of international law that distinguishes it from domestic law is the absence of hierarchical authority. In domestic legal systems, laws are created by legislatures with authority over the entire jurisdiction, applied by courts with mandatory jurisdiction, and enforced by executives commanding police and other enforcement mechanisms. Citizens who violate laws can be prosecuted, fined, imprisoned, or otherwise sanctioned through coercive mechanisms backed by the state's monopoly on legitimate force.
International law lacks all of these features in their full domestic form. There is no world legislature with authority to create binding law over all states without their consent. Courts with compulsory jurisdiction over all states do not exist — jurisdiction is consent-based. And there is no world police force capable of compelling compliance against a determined major power. This is what scholars call the "enforcement gap" in international law.
Despite the enforcement gap, international law works — imperfectly but genuinely — for several reasons. Interest-based compliance explains much of it: many international legal obligations are followed because states find it in their interest to do so. States benefit from the stability and predictability that international legal frameworks provide. A state that systematically violates international agreements undermines the very framework from which it benefits.
Reputational concerns are also powerful. States care about their reputation in the international community. A reputation for keeping commitments is valuable — it makes other states willing to enter into agreements, extend credit, accept diplomatic assurances, and treat the state as a reliable partner. Conversely, a reputation for violating international commitments makes future cooperation more difficult and expensive.
Domestic internalization creates internal enforcement mechanisms. In many states, international law is incorporated into domestic legal systems. Domestic courts apply international law. Domestic agencies are required by legislation to comply with international obligations. Citizens and advocacy groups can sue to enforce international legal requirements. Institutional design can also create compliance incentives through monitoring, transparency, and graduated responses to violations. Treaty bodies that require states to report their compliance, allow third-party monitoring, and shine public light on violations create reputational and political incentives for compliance even without coercive enforcement. Finally, reciprocity creates compliance incentives for many agreements: a state that violates a trade agreement gives the other party grounds to suspend its own commitments.
Enforcement is most problematic when major powers are involved as violators — other states have limited practical ability to compel compliance from the United States, Russia, China, and other major powers, which have at various times ignored or circumvented international legal obligations with limited consequences. Enforcement also fails when short-term interests strongly favor defection over compliance; when agreements lack monitoring mechanisms and violations go undetected or undocumented; and when obligations themselves are vague or contested, providing cover for noncompliance.
The Vienna Convention on Diplomatic Relations was adopted in 1961 at a United Nations conference in Vienna, Austria. It codified customary international law that had governed diplomatic practice for centuries, creating a comprehensive written framework for diplomatic relations. The Convention has been ratified by virtually every country in the world and is considered one of the most successful and universally observed international agreements. It governs the legal status of embassies, the immunities and privileges of diplomats, and the responsibilities of both sending and receiving states.
Article 22: The premises of the diplomatic mission are inviolable. The agents of the receiving State may not enter them, except with the consent of the head of the mission. The receiving State is under a special duty to take all appropriate steps to protect the premises of the mission against any intrusion or damage and to prevent any disturbance of the peace of the mission or impairment of its dignity.
Article 41: All persons enjoying privileges and immunities are under a duty to respect the laws and regulations of the receiving State. They also have a duty not to interfere in the internal affairs of that State. The premises of the mission must not be used in any manner incompatible with the functions of the mission as laid down in the Convention or by other rules of general international law.
These provisions illustrate the tension at the heart of diplomatic immunity. Article 22 gives embassies extraordinary protection — even local law enforcement cannot enter without permission — while Article 41 imposes reciprocal duties of respect and non-interference on diplomats. The two provisions reflect the bargain that makes diplomacy work: sending states receive protection for their missions and personnel, but in exchange their diplomats are supposed to respect their host country's laws and not abuse their privileged position. Real-world cases have tested both provisions. In 1979, Iranian revolutionaries seized the U.S. Embassy in Tehran and held diplomats hostage for 444 days — a profound violation of Article 22 that the international community widely condemned.
Major powers — particularly the United States, Russia, China, France, and the United Kingdom — routinely invoke international law when it supports their positions and ignore or contest it when it constrains them. Critics argue this selective enforcement undermines the legitimacy and effectiveness of international law. Defenders argue that major-power self-interest is an inevitable feature of international relations that must be accommodated rather than wished away.
When powerful states apply international law selectively — insisting on its application against adversaries while exempting themselves and their allies — they corrode the legitimacy of the international legal system. If law applies only to the weak, it is not really law; it is a tool of power. The international community should hold major powers to the same standards as smaller states, even if enforcement is imperfect. Failure to do so breeds cynicism, encourages violation, and creates double standards that weaker states rightly resent.
All legal systems have gaps, enforcement failures, and inequalities of application. The relevant comparison is not between imperfect international law and an ideal of perfect universal enforcement, but between international law and the alternative — no international law at all. Even selectively enforced international norms shape behavior, create expectations, generate diplomatic costs for violations, and constrain some actions by major powers. The existence of international humanitarian law reduces the frequency and severity of certain atrocities even if it does not eliminate them. Perfect should not be the enemy of functional.
Some argue that the solution is institutional reform — strengthening international institutions, expanding compulsory jurisdiction, developing more effective multilateral enforcement mechanisms. Others argue that international law should focus on areas of genuine consensus and shared interest, rather than trying to codify contested norms that major powers will never accept as binding.
Demanding full equal application risks paralysis — if major powers will not accept binding constraints, insisting on them may produce a world with neither effective major-power restraint nor functioning international institutions. Accommodating double standards risks institutionalizing inequality and legitimizing impunity. Most real international legal frameworks occupy an uncomfortable but workable middle ground.
Should the International Criminal Court pursue prosecutions against officials of powerful states that are not parties to the Rome Statute? What factors should guide this decision, and what consequences might different approaches have for the Court's legitimacy and effectiveness?
International law has traditionally been a law of states — creating rights and obligations for governments rather than individuals. But the twentieth and twenty-first centuries have seen a significant expansion of international law's reach toward individuals.
States bear international legal responsibility for how they treat their own citizens and foreign nationals within their territory. International human rights law — built on treaties such as the International Covenant on Civil and Political Rights — creates obligations for governments to respect and protect fundamental rights, obligations that exist regardless of what domestic law says. When states violate these obligations, they are responsible to the international community, not just to their own citizens.
Individuals bear international legal responsibility for certain acts under international criminal law. The principle — established at Nuremberg and developed through the ICC and other international criminal tribunals — is that individuals cannot hide behind state authority to justify participation in genocide, crimes against humanity, or war crimes. "I was following orders" is not a defense to international criminal responsibility.
Citizens, in turn, have both interests in and responsibilities regarding their states' international legal conduct. In democratic systems, citizens can advocate for their governments to ratify international agreements, comply with international legal obligations, and support international institutions. Civil society organizations play an important role in monitoring treaty compliance, documenting violations, advocating for accountability, and mobilizing public pressure. Organizations like Amnesty International, Human Rights Watch, and Transparency International produce the reports and documentation that hold governments accountable — not through legal force, but through information and public attention.
A neighboring country has recently experienced a military coup in which an elected government was overthrown. The new military government has suspended the constitution, arrested opposition leaders, restricted press freedom, and cracked down on protests, resulting in dozens of deaths and hundreds of imprisonments. The country was previously an important trading partner and hosts a significant diplomatic relationship. International organizations have condemned the coup; the United Nations has called for a return to democratic governance. Your government must decide how to respond.
Citizens of the country that experienced the coup (particularly those imprisoned or at risk); business interests that trade with or have investments in the country; your country's government and diplomatic corps; regional neighbors who may be affected by instability; international organizations monitoring the situation; the military government, which controls the country and its security forces; and the deposed government's representatives.
How economically dependent is the country on trade with your state and your trading partners? What are the prospects for multilateral coordination, and do major powers have competing interests? What is the history of sanctions effectiveness in similar situations? What are the humanitarian conditions and what would broad sanctions mean for the civilian population? Are there credible pressure points on the military leadership specifically?
Recommend a policy response to this diplomatic crisis. Identify which combination of approaches you would recommend and why. Explain which stakeholders your approach prioritizes and what tradeoffs you accept. Predict how the military government is likely to respond, and explain how you would adjust your approach if initial measures fail. Write at least two paragraphs defending your recommendation.
International Treaty — Foundational Charter of the United Nations Organization
The United Nations Charter was signed in San Francisco on June 26, 1945, by representatives of 50 nations, entering into force on October 24, 1945. It was drafted in the final months of World War II, when the Allied powers sought to construct an international organization capable of maintaining peace and preventing the catastrophic wars of the twentieth century from recurring. Article 2 sets out the foundational principles that govern the organization and, by extension, are expected to govern the conduct of member states in their international relations. The principles in Article 2 reflect fundamental tensions in the international order: between sovereignty and accountability, between non-interference and human rights, between equality of states and inequality of power.
Article 2(1): The Organization is based on the principle of the sovereign equality of all its Members.
Article 2(3): All Members shall settle their international disputes by peaceful means in such a manner that international peace and security, and justice, are not endangered.
Article 2(4): All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.
Article 2(7): Nothing contained in the present Charter shall authorize the United Nations to intervene in matters which are essentially within the domestic jurisdiction of any state.
Choose a significant international treaty — such as the Paris Agreement on Climate Change (2015), the Nuclear Non-Proliferation Treaty (1968), the United Nations Convention on the Law of the Sea (1982), the Rome Statute of the ICC (1998), the Chemical Weapons Convention (1993), or the Convention on the Rights of the Child (1989) — and investigate it systematically.
Step 1 — Historical background: What problem was the treaty designed to address? What prior events or conditions made agreement possible?
Step 2 — Negotiating process: How were negotiations structured? Who were the key participants? What were the major disagreements, and how were they resolved?
Step 3 — Treaty structure: What are the main obligations the treaty creates? What institutional machinery does it establish? What dispute resolution or enforcement mechanisms does it include?
Step 4 — Ratification record: Which states have ratified the treaty? Which major states have not? What are the stated or evident reasons for non-ratification by holdouts?
Step 5 — Compliance record: How well have parties to the treaty complied with its obligations? Have there been significant violations? How has the international community responded?
Step 6 — Effectiveness assessment: Has the treaty achieved its goals? What evidence supports or challenges a positive assessment? What factors have affected its effectiveness?
Deliverable: A structured research report of 1,500–2,500 words addressing all six questions, accompanied by a one-page policy brief recommending one specific reform or action that would strengthen the treaty's effectiveness going forward.
Chapter 42 has examined the mechanisms through which states negotiate peacefully, make binding commitments, and resolve disputes through law and diplomacy. Chapter 43 will examine what happens when those mechanisms fail — turning to the causes of war, the dynamics of military conflict, the role of alliances and collective security, the management of armed conflict under international humanitarian law, the challenges of peacebuilding, and the tools of arms control and disarmament. The concepts examined in this chapter — sovereignty, treaty obligation, international law, enforcement — will return in new and often more urgent forms when the subject is armed conflict rather than diplomatic exchange. Understanding both chapters together provides the most complete picture of how the international system manages the fundamental challenge of organized violence among sovereign states.
Diplomacy, treaties, and international law are instruments through which humanity attempts to manage the most fundamental political challenge: how do groups of people with different interests, values, and power live together, resolve conflicts, and coordinate action without destroying each other? Domestic governments answer this question within a state's borders through law, institutions, elections, courts, and coercive authority. International diplomacy and law attempt to answer the same question in a world of sovereign states where no such central authority exists.
The system is imperfect. Enforcement is inconsistent. Major powers sometimes escape accountability. Treaties are violated. Diplomacy fails, and conflicts erupt. The international legal order reflects the distribution of power among states as much as it reflects universal principles of justice. These failures are real, and students of government should not romanticize international institutions or mistake the existence of international law for the existence of international justice.
But imperfection is the condition of all political institutions, not the defining feature of international ones. Domestic legal systems also fail to enforce laws consistently, protect powerful interests unfairly, and produce outcomes that fall short of justice. The relevant standard for evaluating international institutions is not perfection but adequacy — do they perform better than the realistic alternatives? By that standard, the international diplomatic and legal order represents a genuine achievement: centuries of accumulated practice, codification, and institutional development that has reduced the frequency of interstate war, extended protections for individuals in conflict, created frameworks for managing shared resources and global challenges, and maintained channels of communication even among adversaries.
For citizens living in a world where climate change, pandemics, trade, migration, arms proliferation, and countless other challenges cross national borders daily, understanding the institutions through which international cooperation is attempted — imperfectly but genuinely — is not a luxury. It is part of the basic civic literacy that democratic participation requires. The agreements governments make in conference rooms in The Hague and Geneva and New York shape the world their citizens inhabit. Knowing how those agreements are made, what makes them work, and what makes them fail is essential knowledge for anyone who cares about how political authority is exercised, challenged, and ultimately justified.